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[vsnet-grb-info 38179] IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40153 SUBJECT: IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/04/16 20:17:54 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-04-16 at 18:32:14.97 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.3036 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140799_37236133.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-04-16 Time: 18:32:14.97 UT RA: 83.1 (+0.57/-0.58 deg 90% PSF containment) J2000 Dec: 15.64 (+0.49/-0.5 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/40153. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38178] IceCube Alert 250416.77: Global MASTER-Net observations report
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40152 SUBJECT: IceCube Alert 250416.77: Global MASTER-Net observations report DATE: 25/04/16 18:39:53 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the IceCube Alert 250416.77 (trigger No 37236133,05h 32m 21.84s , +15d 26m 27.6s, R=0.51) errorbox 18 sec after notice time and 81 sec after trigger time at 2025-04-16 18:33:36 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 75 deg. The sun altitude is -29.8 deg. The galactic latitude b = -9 deg., longitude l = 190 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2845236 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 92 | 2025-04-16 18:33:36 | MASTER-SAAO | (05h 31m 59.71s , +15d 20m 12.0s) | C | 20 | 17.0 | 131 | 2025-04-16 18:34:15 | MASTER-SAAO | (05h 32m 00.24s , +15d 20m 15.4s) | C | 20 | 17.0 | 175 | 2025-04-16 18:34:54 | MASTER-SAAO | (05h 32m 00.81s , +15d 20m 18.5s) | C | 30 | 17.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40152. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38177] IceCube Alert 250416.77: Global MASTER-Net observations report
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40152 SUBJECT: IceCube Alert 250416.77: Global MASTER-Net observations report DATE: 25/04/16 18:39:53 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the IceCube Alert 250416.77 (trigger No 37236133,05h 32m 21.84s , +15d 26m 27.6s, R=0.51) errorbox 18 sec after notice time and 81 sec after trigger time at 2025-04-16 18:33:36 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 75 deg. The sun altitude is -29.8 deg. The galactic latitude b = -9 deg., longitude l = 190 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2845236 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 92 | 2025-04-16 18:33:36 | MASTER-SAAO | (05h 31m 59.71s , +15d 20m 12.0s) | C | 20 | 17.0 | 131 | 2025-04-16 18:34:15 | MASTER-SAAO | (05h 32m 00.24s , +15d 20m 15.4s) | C | 20 | 17.0 | 175 | 2025-04-16 18:34:54 | MASTER-SAAO | (05h 32m 00.81s , +15d 20m 18.5s) | C | 30 | 17.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40152. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38176] Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40151 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB DATE: 25/04/16 16:56:40 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 766511207/250416657 at 15:46:42.41 UT on 16 April 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/40151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38175] GRB 250416B: Fermi GBM Final Real-time Localization
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40150 SUBJECT: GRB 250416B: Fermi GBM Final Real-time Localization DATE: 25/04/16 15:57:09 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 15:46:42 UT on 16 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250416B (trigger 766511207.410564 / 250416657). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 103.8, Dec = -62.2 (J2000 degrees, equivalent to J2000 06h 55m, -62d 12'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 166.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250416657/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250416657/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250416657/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40150. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38174] GRB 250416A: Fermi GBM Final Real-time Localization
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40149 SUBJECT: GRB 250416A: Fermi GBM Final Real-time Localization DATE: 25/04/16 14:17:00 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 14:06:21 UT on 16 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250416A (trigger 766505186.401302 / 250416588). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 323.8, Dec = 70.5 (J2000 degrees, equivalent to J2000 21h 35m, 70d 30'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 111.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250416588/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250416588/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250416588/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40149. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38173] SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40148 SUBJECT: SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart DATE: 25/04/16 09:50:29 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Francis Fortin (IRAP), Diego López-Cámara (UNAM), Jean-Grégoire Ducoin (CPPM), Damien Dornic (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan Watson (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM) and ZiQi Wang (GXU) report: We observed the field of SVOM/ECLAIRs sb25041603 (Wang et al. GCN 40147) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope operated from the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We obtained 50 exposures of 60 s in the i-band starting at 06:39:55 UT on 2025-04-16 (12 min after the onboard trigger, and 16 s after the alert reception). In the stacked image, we do not detect any new source at the ECLAIRs source position (Wang et al. GCN 40147) down to the following 5-sigma limit: i > 22.89 mag (AB) The data were coadded with the Colibrí pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometric calibration was performed using nearby stars from the PanSTARRS DR1 catalog and the magnitude is not corrected for Galactic extinction. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40148. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38172] SVOM/sb25041603: SVOM detection of an X-ray transient
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40147 SUBJECT: SVOM/sb25041603: SVOM detection of an X-ray transient DATE: 25/04/16 07:36:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. Wang (GXU), W. Zheng (UCB), S. Schanne (CEA), M.-G. Bernardini (INAF/LUPM) report on behalf of the SVOM mission team: SVOM/ECLAIRs triggered on the X-ray transient labelled sb25041603 (SVOM burst-id sb25041603) starting at 2025-04-16T06:28:04 UTC (Tb). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced 1 alert with the signal-to-noise-ratio (SNR) of 7.25 in the 5-8 keV energy band over a time window of 655.36 seconds starting at Tb. The localization of the best alert is R.A., Dec 184.1075, 52.6309 degrees: RA (J2000) = 12h16m25.81s Dec (J2000) = 52d37m51.11s with a 90% C.L. radius of 10.81 arcmin (including systematic error of 2 arcmin added in quadrature). We notice the presence of several X-ray transient candidate sources in this error-box, among which the cataclismic variable V* EG UMa located at 9.3 arcmin, but also several quasars, the closest one being 2MASS J12161363+5242459 located at 5.3 arcmin. The detection significance was below the Slew threshold, so no immediate slew was performed on this burst. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocate (BA) on shift for this burst is Ziqi Wang (zq.wang(a)st.gxu.edu.cn). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40147. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38171] Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
by GCN Circulars 16 Apr '25

16 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40146 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB DATE: 25/04/16 07:15:28 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova (MUNI) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 766474855/250416237 at 05:40:50.07 UT on 16 April 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to SAA entry." View this GCN Circular online at https://gcn.nasa.gov/circulars/40146. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38170] IceCube 250414.324: DDOTI Optical Observations
by GCN Circulars 15 Apr '25

15 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40145 SUBJECT: IceCube 250414.324: DDOTI Optical Observations DATE: 25/04/15 13:44:56 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Eleonora Troja (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM) and Margarita Pereyra (UNAM) report: We observe the field of the IceCube 250414.324 (cascade) event with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-15 UTC. DDOTI automatically pointed the region centred in RA, Dec (J2000)= 10:31:34.05 +09:16:36.1, covering about 48% of the IceCube error region. DDOTI observed from 03:18 UTC to 08:35 UTC (from T+19.5 h to T+24.8 h after the trigger) with a total exposure of 1.94 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no uncatalogued sources within the observed field to an average 10-sigma limiting AB magnitude of w > 20.0 This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40145. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38169] GRB 250413A: AstroSat CZTI detection
by GCN Circulars 15 Apr '25

15 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40144 SUBJECT: GRB 250413A: AstroSat CZTI detection DATE: 25/04/15 09:48:34 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a bright long-duration GRB 250413A which was also detected by Konus/Wind (reported through GCN Notices). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-04-13 02:40:16.50 UTC. The measured peak count rate associated with the burst is 225 (+16, -15) counts/s above the background in the combined data of all quadrants, with a total of 4490 (+612, -310) counts. We caution that there is a 0.3 s readout dead time in CZT data during the burst which affects the calculated total counts. The local mean background count rate was 256 (+1, -3) counts/s. Using cumulative rates, we measure a T90 of 75 (+17, -8) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-04-13 02:40:16.24 UTC. The measured peak count rate associated with the burst is 455 (+66, -70) counts/s above the background in the combined data of all quadrants, with a total of 6700 (+786, -821) counts. The local mean background count rate was 1267 (+3, -4) counts/s. We measure a T90 of 74 (+4, -4) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40144. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38168] EP250304a: ATCA radio observations
by GCN Circulars 14 Apr '25

14 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40143 SUBJECT: EP250304a: ATCA radio observations DATE: 25/04/14 19:06:17 GMT FROM: Yuhan Yao at UC Berkeley <yuhanyao(a)berkeley.edu> Authors: Yuhan Yao, AJ Nayana, Eli Wiston, Raffaella Margutti, Ryan Chornock, Wenbin Lu (UC Berkeley), Elizabeth Mahony (CSIRO S&A, Marsfield), Tanmoy Laskar (U of Utah) We observed the Fast X-ray Transient (FXT) EP250304a discovered by Einstein Probe (Chen et al. GCN 39580; Zhang et al. GCN 39591) at the optical counterpart position (Liu et al., GCN 39583) with the Australia Telescope Compact Array at 5.5 and 9 GHz in continuum mode on 2025 March 21st 13:01-17:48 UT (i.e. 17.6 days after the EP trigger) under NAPA program C3623 (PI: Yao). At the redshift of z=0.2 (Saccardi et al., GCN 39585), EP250304a has been associated with a type Ic broad line (Ic-BL) supernova (Izzo et al. GCN 39851). At the optical transient position, we did not detect a radio source at 5.5 GHz. The rms noise in the final map is 15 microJy/beam. The 3-sigma luminosity limit at z=0.2 is Lnu < 5.2 x 10^{28} erg s^{-1} Hz^{-1}. Compared with known Ic-BL SNe with low-luminosity GRB counterparts, the radio upper limit of EP250304a is fainter than that of GRB171205a/SN2017iuk at a similar phase (Leung et al. 2021, MNRAS, 503, 1847), but consistent with those of GRB980425/SN1998bw (Kulkarni et al. 1998, Nature, 395, 663), GRB060218/SN2006aj (Soderberg et al. 2006, Nature, 442, 1014), and GRB100316D/SN2010bh (Margutti et al. 2013, ApJ, 778, 18). View this GCN Circular online at https://gcn.nasa.gov/circulars/40143. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38167] GRB 250412A: AstroSat CZTI detection
by GCN Circulars 14 Apr '25

14 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40142 SUBJECT: GRB 250412A: AstroSat CZTI detection DATE: 25/04/14 06:02:43 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 250412A which was also detected by Fermi GBM (Trigger Num. 766173972). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-12 18:06:07.50 UTC. The measured peak count rate associated with the burst is 109 (+29, -26) counts/s above the background in the combined data of three quadrants (out of four), with a total of 411 (+108, -138) counts. The local mean background count rate was 204 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 6.9 (+2.1, -2.9) s. The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-12 18:06:08 UTC. The measured peak count rate associated with the burst is 219 (+64, -53) counts/s above the background in the combined data of all quadrants, with a total of 768 (+244, -251) counts. The local mean background count rate was 1231 (+6, -7) counts/s. We cannot reliably estimate the T90 for this GRB in the veto detector data. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40142. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38166] GRB 250412A: AstroSat CZTI detection
by GCN Circulars 14 Apr '25

14 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40142 SUBJECT: GRB 250412A: AstroSat CZTI detection DATE: 25/04/14 06:02:43 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 250412A which was also detected by Fermi GBM (Trigger Num. 766173972). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-12 18:06:07.50 UTC. The measured peak count rate associated with the burst is 109 (+29, -26) counts/s above the background in the combined data of three quadrants (out of four), with a total of 411 (+108, -138) counts. The local mean background count rate was 204 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 6.9 (+2.1, -2.9) s. The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-12 18:06:08 UTC. The measured peak count rate associated with the burst is 219 (+64, -53) counts/s above the background in the combined data of all quadrants, with a total of 768 (+244, -251) counts. The local mean background count rate was 1231 (+6, -7) counts/s. We cannot reliably estimate the T90 for this GRB in the veto detector data. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40142. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38165] EP250404a: Nanshan 0.43m Telescope optical observatios
by GCN Circulars 13 Apr '25

13 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40141 SUBJECT: EP250404a: Nanshan 0.43m Telescope optical observatios DATE: 25/04/13 13:41:02 GMT FROM: Abdusamatjan Iskandar at XAO,CAS <abudu(a)xao.ac.cn> S. Yaqup, J.Z. Liu, A. Iskandar, Y. Zhang, A. Esamdin, C.H. Bai, T.H. Zhong (XAO) report on behalf of optical group of the XAO: We observed the field of the EP250404a (Einstein Probe mission, Trigger ID 01709133918) with the 0.43m telescope at Nanshan Station of Xinjiang Astronomical Observatory (XAO). The observations were started at 2025-04-04T14:54:21(UTC), and obtained a series of gri band images. The optical afterglow (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al, GCN 40064; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al, GCN 40073; Taguchi et al., GCN 40074; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085; Pankov et al., GCN 40086; Chu Chen et al., GCN 40088 and Chen et al., GCN 40089) was clearly detected at position R.A. = 125.0606 deg, DEC = 35.5282 deg J2000. The preliminary photometric magnitudes are below: Observation Start-Time T-T0(hr) Exposure Filter Mag. Err. 2025-04-04 14:54:21 0.583 060s g 16.914 0.106 2025-04-04 14:55:56 0.604 060s r 16.067 0.076 2025-04-04 14:57:12 0.626 060s i 15.610 0.080 2025-04-04 14:58:29 0.648 060s g 17.090 0.108 2025-04-04 14:59:48 0.669 060s r 16.294 0.072 2025-04-04 15:01:05 0.690 060s i 15.940 0.105 2025-04-04 15:02:22 0.712 060s g 17.484 0.108 2025-04-04 15:03:41 0.734 060s r 16.398 0.071 2025-04-04 15:04:58 0.755 060s i 15.965 0.099 2025-04-04 15:11:08 0.858 120s i 16.388 0.067 2025-04-04 15:13:25 0.897 120s g 17.690 0.106 2025-04-04 15:15:44 0.934 120s r 17.066 0.077 2025-04-04 15:18:01 0.972 120s i 16.496 0.074 2025-04-04 15:20:19 1.011 120s g 17.735 0.096 2025-04-04 15:22:38 1.049 120s r 17.030 0.059 2025-04-04 15:24:54 1.087 120s i 16.736 0.061 2025-04-04 15:27:12 1.126 120s g 18.184 0.105 2025-04-04 15:29:31 1.164 120s r 17.407 0.070 2025-04-04 15:31:48 1.202 120s i 17.033 0.067 2025-04-04 15:34:27 1.247 200s g 18.252 0.090 2025-04-04 15:52:56 1.554 200s r 17.719 0.085 2025-04-04 15:56:33 1.615 200s i 17.332 0.088 2025-04-05 16:00:10 1.676 200s g 18.508 0.116 2025-04-05 16:03:50 1.736 200s r 18.121 0.087 2025-04-05 16:07:27 1.796 200s i 17.742 0.101 2025-04-05 16:11:04 1.857 200s g 18.335 0.093 2025-04-05 16:14:43 1.917 200s r 17.924 0.070 2025-04-05 16:18:19 1.978 200s i 17.569 0.090 2025-04-05 16:25:36 2.099 200s r 18.261 0.081 2025-04-05 16:36:30 2.280 200s r 18.681 0.117 2025-04-05 16:40:06 2.341 200s i 18.319 0.136 2025-04-05 16:43:45 2.402 200s g 18.815 0.129 2025-04-05 16:47:42 2.467 300s g 18.713 0.123 2025-04-05 16:52:59 2.555 300s r 18.799 0.132 2025-04-05 16:58:16 2.643 300s i 17.798 0.094 2025-04-05 17:03:34 2.732 300s g 19.368 0.188 2025-04-05 17:08:52 2.820 300s r 18.608 0.111 The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40141. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38164] Fermi trigger No 766148493: Global MASTER-Net observations report
by GCN Circulars 13 Apr '25

13 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40140 SUBJECT: Fermi trigger No 766148493: Global MASTER-Net observations report DATE: 25/04/13 12:17:28 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250412.46 (trigger No 766148493,18h 37m 40.08s , -21d 24m 00.0s, R=27.37) errorbox 71363 sec after notice time and 71412 sec after trigger time at 2025-04-13 06:51:41 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 22 deg. The sun altitude is -51.4 deg. The galactic latitude b = -7 deg., longitude l = 13 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2840647 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 71442 | 2025-04-13 06:51:41 | MASTER-OAFA | (16h 41m 59.81s , -14d 00m 54.0s) | C | 60 | 18.9 | 72078 | 2025-04-13 07:02:17 | MASTER-OAFA | (16h 42m 00.36s , -14d 00m 60.0s) | C | 60 | 18.9 | 72712 | 2025-04-13 07:12:51 | MASTER-OAFA | (16h 41m 58.68s , -14d 01m 07.6s) | C | 60 | 18.9 | 73344 | 2025-04-13 07:23:22 | MASTER-OAFA | (16h 41m 58.45s , -14d 01m 17.4s) | C | 60 | 19.0 | 73975 | 2025-04-13 07:33:53 | MASTER-OAFA | (16h 41m 56.43s , -14d 01m 29.7s) | C | 60 | 18.9 | 74436 | 2025-04-13 07:41:44 | MASTER-OAFA | (16h 35m 30.51s , -18d 13m 33.1s) | C | 40 | 17.4 | 74446 | 2025-04-13 07:41:45 | MASTER-OAFA | (16h 45m 08.33s , -17d 49m 39.7s) | C | 60 | 18.9 | 74611 | 2025-04-13 07:44:29 | MASTER-OAFA | (16h 41m 55.83s , -14d 01m 43.6s) | C | 60 | 18.8 | 75080 | 2025-04-13 07:52:28 | MASTER-OAFA | (16h 35m 29.88s , -18d 13m 38.3s) | C | 40 | 17.4 | 75090 | 2025-04-13 07:52:29 | MASTER-OAFA | (16h 45m 07.85s , -17d 49m 44.2s) | C | 60 | 18.8 | 75721 | 2025-04-13 08:03:09 | MASTER-OAFA | (16h 35m 29.19s , -18d 13m 50.2s) | C | 40 | 17.4 | 75731 | 2025-04-13 08:03:09 | MASTER-OAFA | (16h 45m 07.28s , -17d 49m 54.5s) | C | 60 | 18.9 | 76113 | 2025-04-13 08:09:42 | MASTER-OAFA | (16h 40m 23.31s , -12d 33m 39.8s) | C | 40 | 17.3 | 76124 | 2025-04-13 08:09:42 | MASTER-OAFA | (16h 49m 45.59s , -12d 09m 55.2s) | C | 60 | 19.0 | 76352 | 2025-04-13 08:13:41 | MASTER-OAFA | (16h 35m 28.58s , -18d 14m 22.3s) | C | 40 | 17.5 | 76363 | 2025-04-13 08:13:41 | MASTER-OAFA | (16h 45m 06.73s , -17d 50m 26.1s) | C | 60 | 18.9 | 76741 | 2025-04-13 08:20:09 | MASTER-OAFA | (16h 40m 23.12s , -12d 34m 01.7s) | C | 40 | 17.4 | 76751 | 2025-04-13 08:20:09 | MASTER-OAFA | (16h 49m 45.46s , -12d 10m 17.1s) | C | 60 | 19.0 | 76977 | 2025-04-13 08:24:05 | MASTER-OAFA | (16h 35m 28.03s , -18d 14m 44.0s) | C | 40 | 17.4 | 76987 | 2025-04-13 08:24:06 | MASTER-OAFA | (16h 45m 06.25s , -17d 50m 47.6s) | C | 60 | 18.9 | 77365 | 2025-04-13 08:30:34 | MASTER-OAFA | (16h 40m 21.49s , -12d 34m 25.5s) | C | 40 | 17.4 | 77376 | 2025-04-13 08:30:34 | MASTER-OAFA | (16h 49m 43.82s , -12d 10m 40.7s) | C | 60 | 19.0 | 77605 | 2025-04-13 08:34:33 | MASTER-OAFA | (16h 35m 27.53s , -18d 14m 38.7s) | C | 40 | 17.5 | 77615 | 2025-04-13 08:34:33 | MASTER-OAFA | (16h 45m 05.72s , -17d 50m 42.0s) | C | 60 | 18.9 | 78005 | 2025-04-13 08:41:13 | MASTER-OAFA | (16h 40m 20.17s , -12d 34m 52.6s) | C | 40 | 17.3 | 78015 | 2025-04-13 08:41:14 | MASTER-OAFA | (16h 49m 42.55s , -12d 11m 07.5s) | C | 60 | 19.0 | 78081 | 2025-04-13 08:42:30 | MASTER-OAFA | (16h 41m 20.13s , -16d 21m 21.6s) | C | 40 | 17.3 | 78092 | 2025-04-13 08:42:30 | MASTER-OAFA | (16h 50m 52.28s , -15d 57m 29.2s) | C | 60 | 18.8 | 78170 | 2025-04-13 08:43:49 | MASTER-OAFA | (16h 40m 20.39s , -19d 42m 46.1s) | C | 60 | 18.8 | 78633 | 2025-04-13 08:51:41 | MASTER-OAFA | (16h 40m 18.89s , -12d 35m 21.0s) | C | 40 | 17.3 | 78643 | 2025-04-13 08:51:42 | MASTER-OAFA | (16h 49m 41.25s , -12d 11m 35.4s) | C | 60 | 19.0 | 78713 | 2025-04-13 08:53:01 | MASTER-OAFA | (16h 41m 21.18s , -16d 21m 52.5s) | C | 40 | 17.3 | 78723 | 2025-04-13 08:53:01 | MASTER-OAFA | (16h 50m 53.34s , -15d 57m 59.8s) | C | 60 | 18.8 | 78801 | 2025-04-13 08:54:19 | MASTER-OAFA | (16h 40m 20.18s , -19d 43m 30.6s) | C | 60 | 18.8 | 79314 | 2025-04-13 09:03:02 | MASTER-OAFA | (16h 40m 18.08s , -12d 35m 54.6s) | C | 40 | 17.3 | 79324 | 2025-04-13 09:03:02 | MASTER-OAFA | (16h 49m 40.44s , -12d 12m 09.5s) | C | 60 | 19.0 | 79390 | 2025-04-13 09:04:19 | MASTER-OAFA | (16h 41m 18.83s , -16d 22m 11.9s) | C | 40 | 17.3 | 79401 | 2025-04-13 09:04:19 | MASTER-OAFA | (16h 50m 50.92s , -15d 58m 18.8s) | C | 60 | 18.8 | 79479 | 2025-04-13 09:05:37 | MASTER-OAFA | (16h 40m 20.15s , -19d 43m 53.1s) | C | 60 | 18.8 | 79797 | 2025-04-13 09:10:55 | MASTER-OAFA | (16h 36m 33.34s , -21d 36m 50.4s) | C | 60 | 18.8 | 80061 | 2025-04-13 09:15:29 | MASTER-OAFA | (16h 41m 18.16s , -16d 22m 52.3s) | C | 40 | 17.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40140. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38163] Fermi trigger No 766173972: Global MASTER-Net observations report
by GCN Circulars 12 Apr '25

12 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40139 SUBJECT: Fermi trigger No 766173972: Global MASTER-Net observations report DATE: 25/04/12 20:01:03 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250412.75 (trigger No 766173972,23h 19m 21.60s , -81d 40m 12.0s, R=4.38) errorbox 29 sec after notice time and 92 sec after trigger time at 2025-04-12 18:07:39 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 62 deg. The sun altitude is -23.4 deg. The galactic latitude b = -35 deg., longitude l = 307 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2840903 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 103 | 2025-04-12 18:07:39 | MASTER-SAAO | (00h 46m 29.97s , -81d 52m 11.8s) | C | 20 | 16.4 | 128 | 2025-04-12 18:07:39 | MASTER-SAAO | (00h 46m 29.96s , -81d 52m 11.8s) | C | 70 | 17.5 | Coadd 142 | 2025-04-12 18:08:18 | MASTER-SAAO | (00h 46m 30.73s , -81d 52m 12.6s) | C | 20 | 16.8 | 186 | 2025-04-12 18:08:57 | MASTER-SAAO | (00h 46m 31.35s , -81d 52m 13.6s) | C | 30 | 17.1 | 240 | 2025-04-12 18:09:47 | MASTER-SAAO | (00h 46m 32.24s , -81d 52m 14.8s) | C | 40 | 17.1 | 295 | 2025-04-12 18:09:47 | MASTER-SAAO | (00h 46m 32.21s , -81d 52m 14.8s) | C | 150 | 17.9 | Coadd 304 | 2025-04-12 18:10:46 | MASTER-SAAO | (00h 46m 33.63s , -81d 52m 16.4s) | C | 50 | 17.3 | 378 | 2025-04-12 18:11:55 | MASTER-SAAO | (00h 46m 34.57s , -81d 52m 17.7s) | C | 60 | 17.3 | 468 | 2025-04-12 18:13:24 | MASTER-SAAO | (23h 16m 39.62s , -82d 17m 26.5s) | C | 60 | 16.8 | 635 | 2025-04-12 18:16:12 | MASTER-SAAO | (23h 07m 15.27s , -81d 33m 20.6s) | C | 60 | 16.4 | 695 | 2025-04-12 18:16:12 | MASTER-SAAO | (23h 07m 15.34s , -81d 33m 20.6s) | C | 180 | 17.6 | Coadd 714 | 2025-04-12 18:17:30 | MASTER-SAAO | (23h 07m 15.41s , -81d 33m 15.7s) | C | 60 | 17.1 | 793 | 2025-04-12 18:18:49 | MASTER-SAAO | (23h 07m 15.65s , -81d 33m 12.1s) | C | 60 | 17.0 | 872 | 2025-04-12 18:20:08 | MASTER-SAAO | (23h 07m 16.05s , -81d 33m 09.8s) | C | 60 | 17.0 | 1125 | 2025-04-12 18:24:22 | MASTER-SAAO | (00h 39m 40.29s , -82d 33m 58.2s) | C | 60 | 16.6 | 1449 | 2025-04-12 18:29:45 | MASTER-SAAO | (23h 16m 54.42s , -82d 19m 17.7s) | C | 60 | 16.7 | 1528 | 2025-04-12 18:31:05 | MASTER-SAAO | (22h 15m 53.97s , -82d 17m 25.3s) | C | 60 | 16.5 | 1608 | 2025-04-12 18:32:24 | MASTER-SAAO | (23h 16m 36.44s , -82d 18m 37.3s) | C | 60 | 16.8 | 1687 | 2025-04-12 18:33:44 | MASTER-SAAO | (22h 26m 17.48s , -80d 24m 17.0s) | C | 60 | 16.4 | 1766 | 2025-04-12 18:35:03 | MASTER-SAAO | (23h 14m 57.88s , -80d 23m 02.5s) | C | 60 | 16.5 | 1855 | 2025-04-12 18:36:32 | MASTER-SAAO | (00h 39m 46.51s , -82d 35m 00.3s) | C | 60 | 16.8 | 1945 | 2025-04-12 18:38:01 | MASTER-SAAO | (23h 25m 13.11s , -80d 24m 59.7s) | C | 60 | 16.8 | 2035 | 2025-04-12 18:39:31 | MASTER-SAAO | (00h 31m 31.32s , -80d 40m 19.1s) | C | 60 | 17.1 | 2124 | 2025-04-12 18:41:01 | MASTER-SAAO | (23h 17m 06.68s , -82d 19m 06.9s) | C | 60 | 17.1 | 2203 | 2025-04-12 18:42:20 | MASTER-SAAO | (22h 16m 04.94s , -82d 17m 40.7s) | C | 60 | 17.0 | 2283 | 2025-04-12 18:43:39 | MASTER-SAAO | (23h 16m 43.16s , -82d 18m 06.1s) | C | 60 | 17.4 | 2362 | 2025-04-12 18:44:58 | MASTER-SAAO | (22h 26m 24.24s , -80d 23m 23.1s) | C | 60 | 17.3 | 2441 | 2025-04-12 18:46:18 | MASTER-SAAO | (23h 15m 09.95s , -80d 24m 06.0s) | C | 60 | 17.1 | 2530 | 2025-04-12 18:47:47 | MASTER-SAAO | (00h 39m 50.25s , -82d 36m 27.6s) | C | 60 | 17.2 | 2850 | 2025-04-12 18:53:07 | MASTER-SAAO | (23h 25m 21.81s , -80d 25m 00.7s) | C | 60 | 17.1 | 2939 | 2025-04-12 18:54:36 | MASTER-SAAO | (00h 31m 41.67s , -80d 40m 47.8s) | C | 60 | 17.4 | 3028 | 2025-04-12 18:56:05 | MASTER-SAAO | (23h 17m 19.69s , -82d 19m 05.1s) | C | 60 | 17.4 | 3108 | 2025-04-12 18:57:24 | MASTER-SAAO | (22h 16m 15.77s , -82d 18m 00.3s) | C | 60 | 17.6 | 3187 | 2025-04-12 18:58:44 | MASTER-SAAO | (23h 16m 56.52s , -82d 18m 19.9s) | C | 60 | 17.5 | 3267 | 2025-04-12 19:00:03 | MASTER-SAAO | (22h 26m 34.41s , -80d 23m 41.5s) | C | 60 | 17.5 | 3353 | 2025-04-12 19:01:30 | MASTER-SAAO | (23h 15m 20.80s , -80d 24m 20.0s) | C | 60 | 17.4 | 3442 | 2025-04-12 19:02:58 | MASTER-SAAO | (00h 40m 00.06s , -82d 37m 02.6s) | C | 60 | 17.4 | 3533 | 2025-04-12 19:04:30 | MASTER-SAAO | (23h 25m 31.97s , -80d 24m 57.3s) | C | 60 | 17.3 | 3618 | 2025-04-12 19:05:55 | MASTER-SAAO | (00h 14m 03.61s , -80d 22m 51.5s) | C | 60 | 17.4 | 3698 | 2025-04-12 19:07:14 | MASTER-SAAO | (23h 17m 21.18s , -82d 19m 04.4s) | C | 60 | 17.6 | 3777 | 2025-04-12 19:08:33 | MASTER-SAAO | (22h 16m 17.15s , -82d 17m 59.7s) | C | 60 | 17.6 | 3856 | 2025-04-12 19:09:53 | MASTER-SAAO | (23h 17m 00.72s , -82d 18m 23.9s) | C | 60 | 17.5 | 3936 | 2025-04-12 19:11:12 | MASTER-SAAO | (22h 26m 36.06s , -80d 23m 49.6s) | C | 60 | 17.5 | 4015 | 2025-04-12 19:12:32 | MASTER-SAAO | (23h 15m 23.71s , -80d 24m 25.9s) | C | 60 | 17.3 | 4095 | 2025-04-12 19:13:51 | MASTER-SAAO | (00h 18m 08.69s , -82d 18m 44.5s) | C | 60 | 17.6 | 4174 | 2025-04-12 19:15:10 | MASTER-SAAO | (23h 25m 30.83s , -80d 25m 00.8s) | C | 60 | 17.3 | 4253 | 2025-04-12 19:16:30 | MASTER-SAAO | (00h 14m 09.22s , -80d 22m 57.9s) | C | 60 | 17.4 | 4333 | 2025-04-12 19:17:49 | MASTER-SAAO | (23h 17m 28.05s , -82d 19m 02.7s) | C | 60 | 17.5 | 4415 | 2025-04-12 19:19:11 | MASTER-SAAO | (22h 16m 21.76s , -82d 18m 25.1s) | C | 60 | 17.6 | 4494 | 2025-04-12 19:20:31 | MASTER-SAAO | (23h 17m 07.52s , -82d 18m 31.0s) | C | 60 | 17.6 | 4573 | 2025-04-12 19:21:50 | MASTER-SAAO | (22h 26m 39.76s , -80d 24m 00.5s) | C | 60 | 17.5 | 4653 | 2025-04-12 19:23:09 | MASTER-SAAO | (23h 15m 28.97s , -80d 24m 35.3s) | C | 60 | 17.3 | 4732 | 2025-04-12 19:24:29 | MASTER-SAAO | (00h 18m 16.70s , -82d 18m 49.5s) | C | 60 | 17.4 | 4812 | 2025-04-12 19:25:48 | MASTER-SAAO | (23h 25m 37.20s , -80d 25m 14.8s) | C | 60 | 17.4 | 4891 | 2025-04-12 19:27:08 | MASTER-SAAO | (00h 14m 16.02s , -80d 23m 09.7s) | C | 60 | 17.4 | 4971 | 2025-04-12 19:28:27 | MASTER-SAAO | (22h 01m 08.20s , -84d 12m 36.1s) | C | 60 | 17.6 | 5050 | 2025-04-12 19:29:47 | MASTER-SAAO | (23h 22m 16.17s , -84d 12m 32.8s) | C | 60 | 17.6 | 5130 | 2025-04-12 19:31:06 | MASTER-SAAO | (22h 16m 24.57s , -82d 18m 15.7s) | C | 60 | 17.5 | 5209 | 2025-04-12 19:32:26 | MASTER-SAAO | (23h 17m 23.60s , -82d 18m 43.4s) | C | 60 | 17.5 | 5288 | 2025-04-12 19:33:45 | MASTER-SAAO | (22h 26m 43.56s , -80d 26m 17.1s) | C | 60 | 17.6 | 5368 | 2025-04-12 19:35:04 | MASTER-SAAO | (23h 15m 36.28s , -80d 25m 41.7s) | C | 60 | 17.4 | 5447 | 2025-04-12 19:36:23 | MASTER-SAAO | (23h 25m 44.09s , -80d 23m 58.2s) | C | 60 | 17.5 | 5527 | 2025-04-12 19:37:43 | MASTER-SAAO | (00h 14m 22.67s , -80d 24m 57.2s) | C | 60 | 17.5 | 5606 | 2025-04-12 19:39:02 | MASTER-SAAO | (22h 01m 17.48s , -84d 12m 35.9s) | C | 60 | 17.5 | 5685 | 2025-04-12 19:40:22 | MASTER-SAAO | (23h 22m 28.74s , -84d 12m 43.8s) | C | 60 | 17.6 | 5765 | 2025-04-12 19:41:41 | MASTER-SAAO | (23h 04m 31.91s , -84d 12m 56.7s) | C | 60 | 17.5 | 5844 | 2025-04-12 19:43:01 | MASTER-SAAO | (00h 25m 27.62s , -84d 12m 53.1s) | C | 60 | 17.6 | 5927 | 2025-04-12 19:44:23 | MASTER-SAAO | (22h 35m 02.04s , -78d 30m 48.3s) | C | 60 | 17.5 | 6006 | 2025-04-12 19:45:43 | MASTER-SAAO | (23h 15m 42.29s , -78d 31m 29.4s) | C | 60 | 17.1 | 6085 | 2025-04-12 19:47:02 | MASTER-SAAO | (23h 31m 02.44s , -78d 30m 47.0s) | C | 60 | 17.4 | 6165 | 2025-04-12 19:48:21 | MASTER-SAAO | (00h 11m 40.44s , -78d 29m 09.4s) | C | 60 | 17.4 | 6244 | 2025-04-12 19:49:41 | MASTER-SAAO | (22h 01m 22.34s , -84d 13m 42.0s) | C | 60 | 17.5 | 6324 | 2025-04-12 19:51:00 | MASTER-SAAO | (23h 22m 37.77s , -84d 13m 55.3s) | C | 60 | 17.5 | 6403 | 2025-04-12 19:52:19 | MASTER-SAAO | (23h 04m 40.45s , -84d 13m 39.8s) | C | 60 | 17.4 | 6482 | 2025-04-12 19:53:39 | MASTER-SAAO | (00h 25m 47.79s , -84d 11m 23.9s) | C | 60 | 17.5 | 6561 | 2025-04-12 19:54:58 | MASTER-SAAO | (22h 35m 05.70s , -78d 32m 14.7s) | C | 60 | 17.5 | 6640 | 2025-04-12 19:56:17 | MASTER-SAAO | (23h 15m 51.84s , -78d 30m 39.4s) | C | 60 | 16.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40139. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38162] GRB 250411A: DDOTI Optical Observations
by GCN Circulars 12 Apr '25

12 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40138 SUBJECT: GRB 250411A: DDOTI Optical Observations DATE: 25/04/12 15:05:03 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM) and Margarita Pereyra (UNAM) report: We observed the field of the GRB 250411A detected by Fermi/GBM (Fermi GBM Team, GCN 40136) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-12 UTC from 07:13 UTC to 12:05 UTC (from T+12.9 h to T+17.8 h after the trigger) and obtained a total exposure of 1.94 hours. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no evident uncatalogued sources within the observed field to a 10-sigma limiting AB magnitude of: w > 18.93-19.65 This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40138. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38161] Fermi GRB 250411A: Global MASTER-Net observations report
by GCN Circulars 11 Apr '25

11 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40137 SUBJECT: Fermi GRB 250411A: Global MASTER-Net observations report DATE: 25/04/11 20:31:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250411A ( Fermi GBM team, GCN 40136) errorbox 7115 sec after notice time and 7149 sec after trigger time at 2025-04-11 20:16:18 UT, with upper limit up to 17.6 mag. The observations began at zenith distance = 75 deg. The sun altitude is -49.3 deg. The galactic latitude b = 24 deg., longitude l = 1 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2840071 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 7179 | 2025-04-11 20:16:18 | MASTER-SAAO | (16h 18m 59.95s , -13d 56m 46.1s) | C | 60 | 17.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40137. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38160] GRB 250411A: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Apr '25

11 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40136 SUBJECT: GRB 250411A: Fermi GBM Final Real-time Localization DATE: 25/04/11 18:27:41 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 18:17:09 UT on 11 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250411A (trigger 766088234.189348 / 250411762). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 245.7, Dec = -13.9 (J2000 degrees, equivalent to J2000 16h 22m, -13d 54'), with a statistical uncertainty of 3.4 degrees. The angle from the Fermi LAT boresight is 98.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250411762/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250411762/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250411762/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40136. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38159] GRB 250407A: Continued KAIT/Nickel optical observations
by GCN Circulars 11 Apr '25

11 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40135 SUBJECT: GRB 250407A: Continued KAIT/Nickel optical observations DATE: 25/04/11 07:26:26 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> Asia deGraw, Gracelynn Jost, WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, continued the observation of GRB 250407A optical afterglow (Zheng et al., GCN 40116; Ducoin et. al, GCN 40117; Pérez-Fournon et. al, GCN 40125; Pankov et al., GCN 40133) at 03:35 UT, Apr. 09, namely ~1.55 days after burst. A set of clear (roughly R) filter images were obtained. Compared to our earlier observations (Zheng et al., GCN 40116), the reported afterglow had faded to ~20.8 +/- 0.3 mag (Vega) measured in our coadd image. Additional R band images with 600sx5 exposure were obtained with the 1-m Nickel telescopes located at Lick observatory, starting at ~1.55 days after burst. We measure the brightness of R ~ 21.0 +/- 0.2 mag (Vega), similar to the R band magnitude reported by Pankov et al. (GCN 40133) at a slightly later epoch (1.98 days), suggesting that this might be the host galaxy of GRB 250407A as suggested by Ducoin et. al, GCN 40117). View this GCN Circular online at https://gcn.nasa.gov/circulars/40135. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38158] GRB 250314A: e-MERLIN observations
by GCN Circulars 10 Apr '25

10 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40134 SUBJECT: GRB 250314A: e-MERLIN observations DATE: 25/04/10 20:17:58 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> A.L. Thakur [1], G. Bruni [1], L. Piro [1] and G. Gianfagna [1] report: We observed the z=7.3 GRB 250314A (SVOM GCN 39719, VLT/X-shooter GCN 39732, GTC/OSIRIS+ GCN 39743), with the e-MERLIN radio telescope under project RR19004 (PI: Thakur) at 5 GHz starting from Mar 31 (~17 days post-GRB) for three runs of ~12 hours each. 1331+3030 was used for flux scale calibration, and 1332-0509 for complex gain. The beam size was 122x34 milli-arcsec. Data were reduced with the e-MERLIN pipeline and imaged with CASA. The image RMS was 18 uJy/beam. We do not find statistically significant emission at a level above 5-sigma at the position of the NOT counterpart (GCN 39727) or in the broader 2x2 arcsec field. We thus set a 5-sigma upper limit of 90 uJy at 5 GHz. Further e-MERLIN observations are planned. We thank the e-MERLIN director for promptly approving these DDT observations and acknowledge Justin Bray's excellent support in scheduling and executing them. e-MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC, part of UK Research and Innovation. —------------------------ [1] INAF-IAPS View this GCN Circular online at https://gcn.nasa.gov/circulars/40134. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38157] GRB 250407A: Mondy and AbAO Optical Observations
by GCN Circulars 10 Apr '25

10 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40133 SUBJECT: GRB 250407A: Mondy and AbAO Optical Observations DATE: 25/04/10 09:17:26 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN: We observed the field of GRB 250407A detected by Fermi (the Fermi GBM team, GCN 40104; Preis & Greiner, GCN 40105; Mukherjee & Meegan, GCN 40114), SRG (Molkov et. al, GCN 40110), Swift (Evans, GCN 40111; Dichiara et. al, GCN 40113), EP (Zheng et. al, GCN 40119), Konus-Wind (Frederiks et. al, GCN 40121) with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy), and the 0.7-meter AS-32 telescope of the Abastumani Astrophysical Observatory (AbAO). The R-band observations began on 2025-04-08 at 18:01:15 UT, i.e. ~1.12 days since trigger at AbAO. The optical counterpart (Zheng & Fillipenko, GCN 40116; Ducoin et. al, GCN 40117; Pérez-Fournon et. al, GCN 40125) is marginally detected in the stacked image taken with AZT-33IK. The preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err UL Telescope (s) (mid, days) (3sigma) 2025-04-08 18:01:15 89*60 1.12319 R n/d n/d 17.5 AS-32 2025-04-09 14:42:55 34*120 1.97818 R 21.0 0.3 21.2 AZT-33IK Ref. stars USNO-B1.0 RA Dec R2mag 110.81407 36.79950 15.86 110.78017 36.81867 14.55 The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40133. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38156] EP250227a: Further NOT optical observations
by GCN Circulars 10 Apr '25

10 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40132 SUBJECT: EP250227a: Further NOT optical observations DATE: 25/04/10 09:17:11 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> D. B. Malesani (DAWN/NBI and Radboud), J. Sanchez-Sierras (Radboud), P. G. Jonker (Radboud), A. Martin-Carrillo (UCD), A. J. Levan (Radboud and Warwick), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration: We obtained ten 300-s observations in the r band of the field of the fast X-ray transient EP250227a (Wen et al., GCN 39532) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. The mid time was 2025 Apr 5.09 UT (36.9 days after the EP trigger). In Malesani et al. (GCN 39533), based on observations taken 22.4 hr after the EP trigger, we noted a possible optical transient (not consistent with the EP/FXT localisation) within the EP/WXT error circle, revealed by image subtraction using the Legacy survey as template. The new observation was obtained with the same instrument, filter, and pixel scale as our early one, in order to provide a better reference. We then carried out again image subtraction using both ISIS (Alard 2000, A&AS, 144, 363) and PyZOGY (Zackay et al. 2016, doi:10.3847/0004-637X/830/1/27). With the new template, no credible residual is detected at the position of the early optical candidate (Malesani et al., GCN 39533), which we thus consider to be spurious. We set an upper limit r > 23.8 AB to any transient within the EP/WXT error circle, at a time of 22.4 hr after the trigger. In our April 5 observation, one faint object is detected inside the EP/FXT error circle (at coordinates RA = 13:36:34.67, Dec = -13:49:23.18, magnitude r = 24.52 +- 0.23 AB). Its probability of a chance association with the X-ray localization is large. As a result, no connection to EP250227a can be established. View this GCN Circular online at https://gcn.nasa.gov/circulars/40132. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38155] GRB 250320B: cubesat Avion detection
by GCN Circulars 10 Apr '25

10 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40131 SUBJECT: GRB 250320B: cubesat Avion detection DATE: 25/04/10 08:46:40 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2025-03-20 ~23:15:22 UT the long-duration GRB 250320B (Fermi GBM detection: GCN #39792; SVOM detection: GCN #39813, AstroSat CZTI detection: GCN #39808) was detected by the DeCoR-1 instrument on the cubesat Avion of the Moscow University project “Constellation-270” [1]. Total amount of photons detected by Avion is 1350 (energy band 40-500 keV), it corresponds to a fluence of ~6*10^(-6) erg/cm^2 in the range 40-500 keV. LC in the energy range of 40-500 keV has two main episodes with a maximum flux of ~5.8 phot/(cm^2*s) in the 1st peak with a duration of ~13 s, and ~5.2 phot/(cm^2*s) in the 2nd peak with a duration of ~11 s. А total duration (T90) of the burst is ~78 s. The light curve obtained by Avion is available here: https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB20250320_Avion_DeCo… Parameters of GRB 250320B as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en Avion is one of 5 cubesats of the Moscow University project “Constellation-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/40131. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38154] IceCube-250406A: Swift-XRT observations
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40130 SUBJECT: IceCube-250406A: Swift-XRT observations DATE: 25/04/09 14:22:44 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report on behalf of the Swift-XRT team, Swift-XRT observed the field of IceCube-250406A (IceCube Collaboration, GCN 40103) between 22:21 UT on 2025 April 7 and 03:36 UT on 2025 April 8 (85 to 104 ks after the trigger), gathering 4.1 ks over 7 pointings centred on the position from the refined position notice. Three X-ray sources are detected, all of which have counterparts in the 1RXS Rosat catalogue (Voges et al., 1999) and show no sign of elecated flux compared to those data. The sources are: Source 1: Swift J052456.1+170357 at RA, Dec = 81.23375, +17.0660 which is equivalent to: RA (J2000): 05h 24m 56.10s Dec (J2000): +17d 03' 57.8" with an uncertainty of 4.7 arcsec (radius, 90% confidence), and consistent with the position of 1RXS J052456.3+170400. The mean 0.3-10 keV count-rate is 0.030 (+/-0.007) ct/sec, which corresponds to 1.3 (+/-0.3) x 10^-12 erg/cm^2/s. Source 2: Swift J052427.1+172323 at RA, Dec = 81.11301, +17.3898 which is equivalent to: RA (J2000): 05h 24m 27.12s Dec (J2000): +17d 23' 23.2" with an uncertainty of 5.7 arcsec (radius, 90% confidence), and consistent with the position of 1RXS J052425.7+172301. The mean 0.3-10 keV count-rate is 0.051 (+0.016, -0.013) ct/sec, which corresponds to 2.2 (+0.7, -0.6) x 10^-12 erg/cm^2/s. Source 3: Swift J052425.1+172240 at RA, Dec = 81.10483, +17.3780 which is equivalent to: RA (J2000): 05h 24m 25.16s Dec (J2000): +17d 22' 40.9" with an uncertainty of 8.0 arcsec (radius, 90% confidence), and consistent with the position of 1RXS J052425.7+172301 . The mean 0.3-10 keV count-rate is 0.042 (+0.015, -0.012) ct/sec, which corresponds to 1.8 (+0.6, -0.5) x 10^-12 erg/cm^2/s. Note that sources 2 and 3 correspond to the same Rosat source (due to the comparitively large Rosat position errors). In fact, neither source looks particularly point-like and both are within 30" of * 111 Tau -- a fifth magnitude BY Dra star. At this brightness the star will cause optical loading -- the detection of spurious 'X-rays' which are actually an accumulation of optical photons. We therefore view both of these sources with scepticism. A fourth source is also detected, Swift J052440.8+163236 at RA, Dec = 81.17009, 16.5435 degrees and an uncertainty of 8.4 arcsec (radius, 90% confidence). However, this is classified "poor" which corresponds approximately to a 1-sigma detection and is thus likely spurious. The full XRT analysis can be viewed online at https://www.swift.ac.uk/neutrino/NEUTRINO_FIELD00043/. View this GCN Circular online at https://gcn.nasa.gov/circulars/40130. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38153] IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40129 SUBJECT: IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a) DATE: 25/04/09 14:22:43 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, E. Burns on behalf of the IPN, and E. Bozzo, C. Ferrigno, and S. Mereghetti on behalf of the INTEGRAL SPI-ACS GRB team, report: The long-duration GRB 250321D was detected by Konus-Wind in the waiting mode and INTEGRAL (SPI-ACS) at about 22405 s UT (06:13:25), ~200 s after EP triggered on the fast X-ray transient EP250321a (Hu et al., GCNs 39800, 39833). We have triangulated it to a Konus-SPI-ACS annulus centered at RA(2000)=176.654 deg (11h 46m 37s) Dec(2000)=+10.352 deg (+10d 21' 08"), whose radius is 11.845 +/- 11.845 deg (3 sigma). This localization may be improved. EP250321a is inside the annulus and is consistent with the Konus-Wind ecliptic latitude response, lending support to the association of GRB 250321D and the transient. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB250321_T22405/IPN/ The burst time history and spectrum will be given in forthcoming GCN circulars. View this GCN Circular online at https://gcn.nasa.gov/circulars/40129. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38152] AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40128 SUBJECT: AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A DATE: 25/04/09 12:52:44 GMT FROM: Hugo Ayala at Pennsylvania State University <hgayala(a)psu.edu> The AMON, IceCube, and HAWC collaborations report: The AMON NuEm stream channel found a coincidence alert from the IceCube online neutrino selection + HAWC daily monitoring analysis. The analysis looks for IceCube neutrino events -mostly atmospheric in origin- around the position and transit time of a HAWC cluster of likely gamma rays, as identified in the integrated observations from a single transit, in this case having a duration of 6.06 hours. The HAWC transit interval starts from 2025/04/09 04:21:14 UT to 2025/04/09 10:39:53 UT. A total of 6.3 hrs of integrated HAWC time. The location of the coincidence is reported as RA (J2000): 212.8 deg Dec (J2000): 17.2 deg Location uncertainty (50% containment): 0.25 deg (statistical only). Location uncertainty (90% containment): 0.46 deg (statistical only). The false alarm rate (FAR) of this coincidence is 1.05 per year. We encourage follow-up observations of the alert region contingent on the availability of resources and interest, given the quoted FAR. The source 4FGL J1406.9+1643 is the closest to the best position of the coincidence, with a distance of around 1deg. AMON seeks to perform a real-time correlation analysis of the high-energy signals across all known astronomical messengers. More information about AMON can be found in https://www.amon.psu.edu/ Information on the IceCube collaboration: http://icecube.wisc.edu/ Information on the HAWC collaboration: https://www.hawc-observatory.org View this GCN Circular online at https://gcn.nasa.gov/circulars/40128. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38151] IPN triangulation of GRB 250407A
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40127 SUBJECT: IPN triangulation of GRB 250407A DATE: 25/04/09 07:14:45 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, report: The very bright, long-duration GRB 250407A (Fermi-GBM detection: The Fermi GBM team, GCN 40104; Mukherjee and Meegan, GCN 40114; BALROG localization: Preis et al., GCN 40105; SVOM-GRM detection: Wang et al., GCN 40120; Konus-Wind detection: Ferderiks et al., GCN 40121) was detected by Fermi (GBM trigger 765733706), Konus-Wind, and BepiColombo (MGNS) at about 56901 s UT (15:48:21). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 110.410 (07h 21m 38s) +35.618 (+35d 37' 06") Corners: 111.023 (07h 24m 05s) +37.563 (+37d 33' 48") 111.028 (07h 24m 07s) +37.670 (+37d 40' 12") 109.794 (07h 19m 10s) +33.403 (+33d 24' 09") 109.787 (07h 19m 09s) +33.265 (+33d 15' 53") --------------------------------------------- The error box area is 364 sq. arcmin, and its maximum dimension is 4.52 deg (the minimum one is 1.4 arcmin). The Sun distance was 89 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM final (GCN 40104) and BALROG (GCN 40105) localizations. The X-ray transient detected by SRG-ART-XC (GCN 40110) and Swift-XRT (GCN 40113) is inside the box, which further strengthen the interpretation of the transient as the burst afterglow. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB250407_T56895/IPN View this GCN Circular online at https://gcn.nasa.gov/circulars/40127. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38150] EP250407a: Global MASTER-Net observations report
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40126 SUBJECT: EP250407a: Global MASTER-Net observations report DATE: 25/04/08 23:27:52 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250407a ( EP Team et al., GCN 40118) errorbox 49972 sec after notice time and 85240 sec after trigger time at 2025-04-08 23:08:03 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 18 deg. The sun altitude is -10.6 deg. The galactic latitude b = 5 deg., longitude l = 262 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2836941 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 85271 | 2025-04-08 23:08:03 | MASTER-OAFA | (08h 59m 01.05s , -38d 53m 39.6s) | C | 60 | 18.2 | 85448 | 2025-04-08 23:11:01 | MASTER-OAFA | (08h 59m 05.07s , -38d 53m 10.9s) | C | 60 | 18.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40126. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38149] GRB 250407A: LCO detection of a fading optical counterpart
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40125 SUBJECT: GRB 250407A: LCO detection of a fading optical counterpart DATE: 25/04/08 21:48:17 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) Following the detection by Fermi GBM of the bright and likely long Gamma-Ray Burst GRB 250407A (Fermi GBM team, GCN circ. 40104; Preis and Greiner, GCN circ. 40105; and Mukherjee et al., GCN circ. 40114) and the associated X-ray afterglow by SRG/ART-XC (Molkov et al., GCN circ. 40110), we observed the field with the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Observatory (Tenerife, Spain) in the SDSS g, r, and i filters. The observations started at 2025-04-07 21:06:04 UTC, about 5.29 hours after the Fermi trigger. We detect the optical afterglow in the r and i filters, but not in the g filter, at the position reported by Zheng and Filippenko (GCN circ. 40116) and Ducoin et al. (GCN circ. 40117), that is consistent within the errors with the SRG/ART-XC (Molkov et al., GCN circ. 40110), Swift-XRT (Dichiara et al., GCN circ. 40113) and EP-WXT (Zheng et al., GCN circ. 40119) X-ray afterglow positions. GRB 250407A has also been detected by SVOM/GRM (Wang et al., GCN circ. 40120) and Konus-Wind (Frederiks et al., GCN circ. 40121). A fading of the optical brightness between our LCOGT observations and those of KAIT (Zheng and Filippenko, GCN circ. 40116) and COLIBRÍ/DDRAGO (Ducoin et al., GCN circ. 40117) is detected. We measure the following preliminary r and i magnitudes and limiting (5-sigma) g-band magnitude, calibrated against Pan-STARRS DR2 stars, that are not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) | limiting magnitude (5 sigma) ------------------------------------------------------------------------------------------------------ 2025-04-07 21:06:04 19.67 0.11 r 300 ----- 2025-04-07 21:10:26 ----- ---- g 180 20.45 2025-04-07 22:01:01 19.92 0.20 r 180 ----- 2025-04-07 22:15:32 19.53 0.19 i 180 ----- This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38148] Fermi-LAT gamma-ray observations of IceCube-250406A
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40124 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-250406A DATE: 25/04/08 19:44:10 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), C. Bartolini (INFN Bari), S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250406A neutrino event (GCN 40103) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-04-06 at 22:50:35.34 UTC (T0) with J2000 position RA = 81.47 (+0.54, -0.53) deg, Decl. = 16.96 (+0.42, -0.50) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC250406A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250406A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250406A best-fit position, the >100 MeV flux upper limit (95% confidence) is <1.72e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <2.13e-08 (<1.58e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. The closest catalogued gamma-ray source to the IC250406A best-fit position is 4FGL J0521.2+1637 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), associated with the compact steep spectrum quasar 3C 138, located approximately 1.15° away from the IceCube event, outside the 90% neutrino localization region. Since October 2024, the source has exhibited strong and prolonged gamma-ray flaring activity (see ATel #16845, ATel #17107). A preliminary analysis confirms that this enhanced activity is ongoing, with a daily averaged gamma-ray flux (E > 100 MeV) of (0.39± 0.29) × 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), as observed on April 6, 2025. This represents an increase in flux by a factor of approximately 93 compared to the average flux reported in the 4FGL-DR4. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/40124. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38147] EP250407a: Swift-XRT observations
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40123 SUBJECT: EP250407a: Swift-XRT observations DATE: 25/04/08 19:20:26 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> M. A. Williams (PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: We have analyzed 2100 s of XRT data for the recently reported transient EP250407a (GCN #40118), from T0+36.5 ks to T0+42.4 ks after detection by Einstein Probe WXT. The data are entirely in Photon Counting (PC) mode. No X-ray sources have been detected within the estimated 90% EP-WXT error region (2.5 arcmin), with an upper limit on count rate of 5.3 × 10^-3 ct/s. For a typical GRB-like spectrum, this equates to an upper limit on flux of 2 x 10^-13 erg/s/cm^2 (0.3-10 keV). The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/EP/EP_FIELD00033/. View this GCN Circular online at https://gcn.nasa.gov/circulars/40123. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38146] IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40122 SUBJECT: IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/04/08 19:18:55 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-250406A (https://gcn.nasa.gov/circulars/40103) in a time range of 1000 seconds centered on the alert event time (2025-04-06 22:42:15.340 UTC to 2025-04-06 22:58:55.340 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-250406A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250406A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 9e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-04-05 22:50:35.340 UTC to 2025-04-07 22:50:35.340 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250406A is 1.6e-01 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/40122. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38145] Konus-Wind detection of GRB 250407A
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40121 SUBJECT: Konus-Wind detection of GRB 250407A DATE: 25/04/08 16:13:31 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250407A ( Fermi-GBM detection: The Fermi GBM team, GCN 40104; Mukherjee & Meegan, GCN 40114; SVOM/GRM observation: Wang et al., GCN 20120) triggered Konus-Wind (KW) at T0=56895.249 s UT (15:48:15.249). The burst afterglow was detected and localized by SRG/ART-XC (Molkov et al. 2025, GCN 40110) and Swift-XRT (Dichiara et al. 2025, GCN 40113). The burst light curve shows a bright pulse which starts at ~T0-6 s and has a total duration of ~20 s. A weaker emission can be traced at least to ~T0+50 s. The emission in the main pulse is seen up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250407_T56895/ As observed by Konus-Wind, the burst had a fluence of (1.57 ± 0.04)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 5.292 s, of (1.41 ± 0.05)x10^-4 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+15.616 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -1.02 (-0.03,+0.03), the high energy photon index beta = -2.27 (-0.07,+0.06), the peak energy Ep = 648 (-44,+46) keV, chi2 = 162/97 dof. The spectrum near the peak count rate (measured from T0+5.888 s to T0+7.424 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.76 (-0.06,+0.07), the high energy photon index beta = -2.38 (-0.14,+0.11), the peak energy Ep = 833 (-99,+106) keV, chi2 = 78/65 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40121. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38144] GRB 250407A: SVOM/GRM observation of a bright long burst
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40120 SUBJECT: GRB 250407A: SVOM/GRM observation of a bright long burst DATE: 25/04/08 14:40:37 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Marius Brunet, Jean-Luc Atteia, Hui Yang (IRAP), Maria-Grazia Bernardini (INAF-OAB), Stéphane Schanne (CEA), Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250407A (SVOM trigger reference: sb25040701) at 2025-04-07T15:48:13.000 (T0). This burst was also detected by Fermi/GBM (Fermi GBM Team, GCN 40104). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 11.1 +0.2/-0.3 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250407A.png In addition, ECLAIRs onboard trigger also detected a very significant increase of the count-rates at the time of the burst, but the detector plane image is not correlated with the mask pattern. This confirmed that the position of this burst, which is determined by Swift/XRT (GCN 40113, RA: 110.75876 deg, DEC: 36.79827 deg, Error: 2.8 arcsec), located at about 45.6 degrees from the SVOM optical axis, and was just outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0 to T0+18 s is best fitted by Band function. The alpha is -0.90 +/- 0.01, beta is -2.27 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 569 +/- 27 keV. The event fluence (10-1000 keV) in this time interval is (1.08 +/- 0.01)E-04 erg/cm^2. Thus GRB 250407A is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250407A_amati.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40120. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38143] GRB 250407A: EP-WXT afterglow detection
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40119 SUBJECT: GRB 250407A: EP-WXT afterglow detection DATE: 25/04/08 09:47:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. C. Zheng, D. F. Hu (PMO, CAS), X. Mao, W. X. Wang, W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of the X-ray afterglow of GRB 250407A by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. In an observation starting at 2025-04-07T17:11:31.158 (UTC), WXT detected an uncatalogued X-ray source at a position R.A. = 110.767 deg, DEC = 36.800 deg (J2000) with an uncertainty of 2.7 arcmin (radius, 90% C.L. statistical and systematic). This source is only 25 arcsec away from the X-ray afterglow of GRB 250407A that was detected by Swift/XRT (GCN 40113). The WXT observation started about 83 minutes after the trigger of GRB 250407A by Fermi/GBM (GCN 40104). The temporal and spatial coincidence suggests that WXT likely detected the X-ray afterglow of GRB 250407A. The observation lasted for 422 seconds, during which no significant variation was observed. The time-averaged spectrum can be fitted with an absorbed powerlaw model, with a photon index of 1.5(-0.7/+0.8), while nH is fixed at the Galactic value of 7.1 x 10^20 cm^-2. The unabsorbed 0.5-4 keV flux is estimated to be 2.0 (-0.7/+1.2) x 10^-10 erg/s/cm^2. The uncertainties are quoted at the 90% confidence level for the above spectral parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/40119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38142] EP250407a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40118 SUBJECT: EP250407a: EP-WXT detection of a fast X-ray transient DATE: 25/04/08 09:13:36 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. F. Hu, T. C. Zheng (PMO, CAS), X. Mao, W. X. Wang, W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient EP250407a detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2025-04-07T23:27:23 (UTC) and lasted for about 70s. We apologize that an incorrect trigger date was reported in the GCN Notice (trigger ID: 11916648441). The WXT position of EP250407a is R.A.= 134.813 deg, DEC = -38.956 deg (J2000) with an uncertainty of 2.5 arcmin (radius, 90% C.L. statistical and systematic). No known X-ray sources are found within the WXT error circle. The average 0.5-4 keV spectrum can be fitted with an absorbed powerlaw with a photon index of 1.4 (+/-0.6) and a fixed Galactic hydrogen column density of 4.67 x 10^21 cm^-2. We derive an average unabsorbed flux of 4.7(-1.0/+1.2) x 10^(-9) erg/s/cm^2, and a peak flux of approximately 1.0 x 10^(-8) erg/s/cm^2 (both in 0.5-4 keV). A follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP is planned. Further follow-up observations are encouraged to identify the nature of this X-ray transient. The contact TA of this source is Ding-Fang Hu, please contact him via the email dfhu(a)pmo.ac.cn if needed. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/40118. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38141] GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40117 SUBJECT: GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart DATE: 25/04/08 08:55:29 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Camila Angulo (UNAM), Stéphane Basa (UAR Pytheas), Rosa L. Becerra (U Roma), William H. Lee (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of GRB 250407A (Fermi GBM team, GCN Circ. 40104; Preis et al., GCN Circ. 40105) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-08 UTC. We observed from 03:01 to 03:53 UTC (11.21 to 12.09 hours after the trigger) and obtained 20 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. At the position reported previously by SRG/ART-XC (Molkov et al. GCN Circ. 40110) and Swift/XRT (Evans et al., GCN Circ. 40113), we detect a source with a magnitude of i = 19.96 +/- 0.03, consistent with the value reported by Zheng et al. (GCN Circ. 40116). In this position, there is a previously identified source (ID: 152151107588088917) in the Pan-STARRS catalog with a PSF magnitude of i = 22.99 +/- 0.14. We propose that this is the host galaxy of GRB 250407A. Further observations are planned. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40117. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38140] GRB 250407A: KAIT Optical Afterglow Candidate
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40116 SUBJECT: GRB 250407A: KAIT Optical Afterglow Candidate DATE: 25/04/08 05:41:09 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 250407A (GBM team, GCN 40104; Preis et al., GCN 40105; Mukherjee et al., GCN 40114) around the X-ray afterglow location (Molkov et al., GCN 40110; Dichiara et al., GCN 40113) starting at 04:17, Apr. 08 UT, about 12.48 hours after the burst. A set of clear (roughly R) filter images were obtained. Within the XRT afterglow (Dichiara et al., GCN 40113) error circle, we detected an uncataloged optical afterglow candidate at J2000 position of (error ~0.5"): RA: 07:23:02.11 Dec: +36:47:54.97 We estimate the clear band magnitude to be ~20.1 +/- 0.3 mag (Vega) at 12.48 hours after the burst. Further observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/40116. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38139] IceCube-250406A: No candidates from the Zwicky Transient Facility
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40115 SUBJECT: IceCube-250406A: No candidates from the Zwicky Transient Facility DATE: 25/04/08 01:35:32 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Jannis Necker (DESY), Akshay Eranhalodi (DESY), Robert Stein (JSI), Anna Franckowiak (Ruhr University Bochum) and Jesper Sollerman (Stockholm) report: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-250406A (Zegarelli et. al, GCN 40103) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2025-04-07 03:54 UTC, approximately 5.1 hours after event time. We covered 69.0% (0.6 sq deg) of the reported localization region. This includes 10.1% (0.1 sq deg) at galactic latitude < 10 deg. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). No candidate counterparts were detected. This is consistent with non-detections reported by other optical telescopes (Becerra et al, GCN 40101, 40102, 40108). Observations of this field will continue as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/40115. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38138] GRB 250407A: Fermi GBM Detection
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40114 SUBJECT: GRB 250407A: Fermi GBM Detection DATE: 25/04/08 01:28:16 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 15:48:21.07 UT on 07 April 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250407A (trigger 765733706/250407659). The afterglow was detected by ART-XC (Molkov et al. 2025, GCN 40110) and Swift-XRT (Dichiara et al. 2025, GCN 40113). The Fermi GBM Final Localization (GCN 40104) is consistent with the ART-XC and Swift-XRT positions. The angle from the Fermi LAT boresight is 116 degrees. The GBM light curve consists of a single-peak emission episode with a duration (T90) of about 6.3 s (50-300 keV). The time-averaged spectrum from T0+0.6 to T0+5.1 s is best fit by a Band function with Epeak = 470 +/- 20 keV, alpha = -0.18 +/- 0.03, and beta = -2.08 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (2.65 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 62.4 +/- 0.7 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40114. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38137] GRB 250407A: Swift-XRT afterglow detection
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40113 SUBJECT: GRB 250407A: Swift-XRT afterglow detection DATE: 25/04/08 00:14:46 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), D.N. Burrows (PSU), M. A. Williams (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 250407A (GCN circ. 40104, GCN circ. 40105). We searched for X-ray sources in 293 s of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 293 s, obtained between T0+18.8 ks and T0+19.1 ks. An uncatalogued X-ray source is detected within the estimated 3-sigma Fermi/GBM error region (29 arcsec) and is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 293 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 110.75876, +36.79827 which is equivalent to: RA (J2000): 07h 23m 02.10s Dec(J2000): +36d 47' 53.8" with an uncertainty of 2.8 arcsec (radius, 90% confidence). This position is 6.9 arcsec from the SRG/ART-XC position reported by Molkov et al (GCN circ. 40110). We note that the source has faded since the SRG/ART-XC observation. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.8 (+0.4, -0.3). The best-fitting absorption column is 3.0 (+1.7, -1.4) x 10^21 cm^-2, in excess of the Galactic value of 7.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.0 (+1.7, -1.4) x 10^21 cm^-2 Galactic foreground: 7.0 x 10^20 cm^-2 Excess significance: 2.8 sigma Photon index: 1.8 (+0.4, -0.3) The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021826/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021826. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40113. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38136] Fermi GRB 250407A: Global MASTER-Net observations report
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40112 SUBJECT: Fermi GRB 250407A: Global MASTER-Net observations report DATE: 25/04/07 22:31:13 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250407A ( Fermi GBM team, GCN 40104) errorbox 27 sec after notice time and 46 sec after trigger time at 2025-04-07 15:49:07 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 42 deg. The sun altitude is -29.6 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250407A errorbox 4363 sec after notice time and 4383 sec after trigger time at 2025-04-07 17:01:24 UT, with upper limit up to 16.1 mag. Observations started at twilight. The observations began at zenith distance = 19 deg. The sun altitude is -14.4 deg. The galactic latitude b = 24 deg., longitude l = 176 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2835912 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 52 | 2025-04-07 15:49:07 | MASTER-Tunka | (07h 31m 43.27s , +43d 36m 20.3s) | C | 10 | 16.5 | 594 | 2025-04-07 15:58:06 | MASTER-Tunka | (07h 18m 01.14s , +44d 15m 13.8s) | C | 15 | 16.8 | 609 | 2025-04-07 15:58:06 | MASTER-Tunka | (07h 18m 01.11s , +44d 15m 13.8s) | C | 45 | 17.3 | Coadd 612 | 2025-04-07 15:58:25 | MASTER-Tunka | (07h 18m 01.10s , +44d 15m 13.6s) | C | 15 | 16.8 | 631 | 2025-04-07 15:58:43 | MASTER-Tunka | (07h 18m 01.05s , +44d 15m 13.2s) | C | 15 | 16.9 | 650 | 2025-04-07 15:59:02 | MASTER-Tunka | (07h 18m 00.98s , +44d 15m 12.7s) | C | 15 | 16.8 | 665 | 2025-04-07 15:59:02 | MASTER-Tunka | (07h 18m 00.96s , +44d 15m 12.7s) | C | 45 | 17.5 | Coadd 668 | 2025-04-07 15:59:21 | MASTER-Tunka | (07h 18m 00.92s , +44d 15m 12.2s) | C | 15 | 16.9 | 687 | 2025-04-07 15:59:40 | MASTER-Tunka | (07h 18m 00.86s , +44d 15m 11.4s) | C | 15 | 17.1 | 706 | 2025-04-07 15:59:58 | MASTER-Tunka | (07h 18m 00.82s , +44d 15m 10.8s) | C | 15 | 17.0 | 721 | 2025-04-07 15:59:58 | MASTER-Tunka | (07h 18m 00.81s , +44d 15m 10.7s) | C | 45 | 17.5 | Coadd 724 | 2025-04-07 16:00:17 | MASTER-Tunka | (07h 18m 00.77s , +44d 15m 10.6s) | C | 15 | 16.9 | 742 | 2025-04-07 16:00:35 | MASTER-Tunka | (07h 18m 00.71s , +44d 15m 10.3s) | C | 15 | 16.9 | 761 | 2025-04-07 16:00:54 | MASTER-Tunka | (07h 18m 00.68s , +44d 15m 10.0s) | C | 15 | 17.0 | 776 | 2025-04-07 16:00:54 | MASTER-Tunka | (07h 18m 00.65s , +44d 15m 09.9s) | C | 45 | 17.4 | Coadd 779 | 2025-04-07 16:01:12 | MASTER-Tunka | (07h 18m 00.61s , +44d 15m 09.7s) | C | 15 | 16.9 | 799 | 2025-04-07 16:01:31 | MASTER-Tunka | (07h 18m 00.55s , +44d 15m 09.2s) | C | 15 | 16.6 | 817 | 2025-04-07 16:01:50 | MASTER-Tunka | (07h 18m 00.46s , +44d 15m 08.1s) | C | 15 | 16.4 | 832 | 2025-04-07 16:01:50 | MASTER-Tunka | (07h 18m 00.45s , +44d 15m 08.0s) | C | 45 | 16.6 | Coadd 835 | 2025-04-07 16:02:08 | MASTER-Tunka | (07h 18m 00.45s , +44d 15m 07.8s) | C | 15 | 16.3 | 854 | 2025-04-07 16:02:27 | MASTER-Tunka | (07h 18m 00.39s , +44d 15m 07.6s) | C | 15 | 16.2 | 870 | 2025-04-07 16:02:45 | MASTER-Tunka | (07h 18m 00.33s , +44d 15m 07.3s) | C | 10 | 15.9 | 880 | 2025-04-07 16:02:45 | MASTER-Tunka | (07h 18m 00.32s , +44d 15m 07.3s) | C | 30 | 16.6 | Coadd 883 | 2025-04-07 16:02:58 | MASTER-Tunka | (07h 18m 00.28s , +44d 15m 07.0s) | C | 10 | 16.0 | 896 | 2025-04-07 16:03:12 | MASTER-Tunka | (07h 18m 00.22s , +44d 15m 07.0s) | C | 10 | 16.2 | 910 | 2025-04-07 16:03:25 | MASTER-Tunka | (07h 18m 00.20s , +44d 15m 06.6s) | C | 10 | 16.2 | 920 | 2025-04-07 16:03:25 | MASTER-Tunka | (07h 18m 00.20s , +44d 15m 06.6s) | C | 30 | 16.5 | Coadd 924 | 2025-04-07 16:03:39 | MASTER-Tunka | (07h 18m 00.21s , +44d 15m 07.0s) | C | 10 | 16.2 | 937 | 2025-04-07 16:03:53 | MASTER-Tunka | (07h 18m 00.17s , +44d 15m 06.7s) | C | 10 | 16.2 | 951 | 2025-04-07 16:04:06 | MASTER-Tunka | (07h 18m 00.16s , +44d 15m 06.5s) | C | 10 | 16.2 | 961 | 2025-04-07 16:04:06 | MASTER-Tunka | (07h 18m 00.15s , +44d 15m 06.5s) | C | 30 | 16.8 | Coadd 964 | 2025-04-07 16:04:20 | MASTER-Tunka | (07h 18m 00.11s , +44d 15m 06.2s) | C | 10 | 16.3 | 978 | 2025-04-07 16:04:33 | MASTER-Tunka | (07h 18m 00.08s , +44d 15m 05.8s) | C | 10 | 16.4 | 992 | 2025-04-07 16:04:47 | MASTER-Tunka | (07h 18m 00.06s , +44d 15m 05.5s) | C | 10 | 16.5 | 1002 | 2025-04-07 16:04:47 | MASTER-Tunka | (07h 18m 00.06s , +44d 15m 05.4s) | C | 30 | 16.9 | Coadd 1005 | 2025-04-07 16:05:01 | MASTER-Tunka | (07h 18m 00.03s , +44d 15m 05.1s) | C | 10 | 16.5 | 1019 | 2025-04-07 16:05:14 | MASTER-Tunka | (07h 17m 59.92s , +44d 15m 04.5s) | C | 10 | 16.3 | 1032 | 2025-04-07 16:05:28 | MASTER-Tunka | (07h 17m 59.88s , +44d 15m 04.1s) | C | 10 | 16.2 | 1042 | 2025-04-07 16:05:28 | MASTER-Tunka | (07h 17m 59.88s , +44d 15m 04.0s) | C | 30 | 16.6 | Coadd 1046 | 2025-04-07 16:05:42 | MASTER-Tunka | (07h 17m 59.83s , +44d 15m 03.8s) | C | 10 | 16.1 | 1060 | 2025-04-07 16:05:56 | MASTER-Tunka | (07h 17m 59.82s , +44d 15m 03.7s) | C | 10 | 16.1 | 1074 | 2025-04-07 16:06:09 | MASTER-Tunka | (07h 17m 59.75s , +44d 15m 03.5s) | C | 10 | 16.1 | 1084 | 2025-04-07 16:06:09 | MASTER-Tunka | (07h 17m 59.75s , +44d 15m 03.6s) | C | 30 | 16.6 | Coadd 1087 | 2025-04-07 16:06:23 | MASTER-Tunka | (07h 17m 59.74s , +44d 15m 03.4s) | C | 10 | 16.2 | 1101 | 2025-04-07 16:06:37 | MASTER-Tunka | (07h 17m 59.68s , +44d 15m 03.0s) | C | 10 | 16.2 | 1115 | 2025-04-07 16:06:50 | MASTER-Tunka | (07h 17m 59.64s , +44d 15m 03.1s) | C | 10 | 16.4 | 1125 | 2025-04-07 16:06:50 | MASTER-Tunka | (07h 17m 59.64s , +44d 15m 03.1s) | C | 30 | 17.0 | Coadd 1128 | 2025-04-07 16:07:04 | MASTER-Tunka | (07h 17m 59.60s , +44d 15m 02.5s) | C | 10 | 16.5 | 1142 | 2025-04-07 16:07:17 | MASTER-Tunka | (07h 17m 59.60s , +44d 15m 01.8s) | C | 10 | 16.7 | 1156 | 2025-04-07 16:07:31 | MASTER-Tunka | (07h 17m 59.57s , +44d 15m 02.0s) | C | 10 | 16.7 | 1166 | 2025-04-07 16:07:31 | MASTER-Tunka | (07h 17m 59.57s , +44d 15m 01.9s) | C | 30 | 17.3 | Coadd 1169 | 2025-04-07 16:07:45 | MASTER-Tunka | (07h 17m 59.54s , +44d 15m 02.1s) | C | 10 | 16.8 | 1183 | 2025-04-07 16:07:58 | MASTER-Tunka | (07h 17m 59.49s , +44d 15m 01.4s) | C | 10 | 16.8 | 1199 | 2025-04-07 16:08:12 | MASTER-Tunka | (07h 17m 59.47s , +44d 15m 01.1s) | C | 15 | 16.8 | 1214 | 2025-04-07 16:08:12 | MASTER-Tunka | (07h 17m 59.45s , +44d 15m 01.1s) | C | 45 | 17.4 | Coadd 1218 | 2025-04-07 16:08:30 | MASTER-Tunka | (07h 17m 59.40s , +44d 15m 00.9s) | C | 15 | 16.7 | 1237 | 2025-04-07 16:08:49 | MASTER-Tunka | (07h 17m 59.37s , +44d 15m 00.1s) | C | 15 | 16.9 | 1255 | 2025-04-07 16:09:08 | MASTER-Tunka | (07h 17m 59.35s , +44d 15m 00.0s) | C | 15 | 17.0 | 1270 | 2025-04-07 16:09:08 | MASTER-Tunka | (07h 17m 59.35s , +44d 15m 00.1s) | C | 45 | 17.6 | Coadd 1274 | 2025-04-07 16:09:27 | MASTER-Tunka | (07h 17m 59.31s , +44d 14m 59.5s) | C | 15 | 17.2 | 1293 | 2025-04-07 16:09:46 | MASTER-Tunka | (07h 17m 59.25s , +44d 14m 59.2s) | C | 15 | 17.2 | 1312 | 2025-04-07 16:10:04 | MASTER-Tunka | (07h 17m 59.17s , +44d 14m 58.5s) | C | 15 | 17.0 | 1327 | 2025-04-07 16:10:04 | MASTER-Tunka | (07h 17m 59.16s , +44d 14m 58.3s) | C | 45 | 17.5 | Coadd 1330 | 2025-04-07 16:10:22 | MASTER-Tunka | (07h 17m 59.11s , +44d 14m 58.2s) | C | 15 | 16.9 | 1349 | 2025-04-07 16:10:41 | MASTER-Tunka | (07h 17m 59.07s , +44d 14m 58.1s) | C | 15 | 17.1 | 1367 | 2025-04-07 16:11:00 | MASTER-Tunka | (07h 17m 59.06s , +44d 14m 57.8s) | C | 15 | 17.1 | 1382 | 2025-04-07 16:11:00 | MASTER-Tunka | (07h 17m 59.03s , +44d 14m 57.5s) | C | 45 | 17.6 | Coadd 1386 | 2025-04-07 16:11:19 | MASTER-Tunka | (07h 17m 58.96s , +44d 14m 56.9s) | C | 15 | 17.0 | 1405 | 2025-04-07 16:11:37 | MASTER-Tunka | (07h 17m 58.88s , +44d 14m 56.5s) | C | 15 | 16.9 | 1423 | 2025-04-07 16:11:56 | MASTER-Tunka | (07h 17m 58.84s , +44d 14m 56.1s) | C | 15 | 17.0 | 1438 | 2025-04-07 16:11:56 | MASTER-Tunka | (07h 17m 58.82s , +44d 14m 55.9s) | C | 45 | 17.7 | Coadd 1442 | 2025-04-07 16:12:14 | MASTER-Tunka | (07h 17m 58.77s , +44d 14m 55.3s) | C | 15 | 17.1 | 1460 | 2025-04-07 16:12:33 | MASTER-Tunka | (07h 17m 58.72s , +44d 14m 55.3s) | C | 15 | 17.0 | 1479 | 2025-04-07 16:12:52 | MASTER-Tunka | (07h 17m 58.66s , +44d 14m 55.3s) | C | 15 | 17.1 | 1494 | 2025-04-07 16:12:52 | MASTER-Tunka | (07h 17m 58.65s , +44d 14m 55.2s) | C | 45 | 17.6 | Coadd 1498 | 2025-04-07 16:13:10 | MASTER-Tunka | (07h 17m 58.60s , +44d 14m 54.3s) | C | 15 | 17.0 | 1516 | 2025-04-07 16:13:29 | MASTER-Tunka | (07h 17m 58.58s , +44d 14m 54.0s) | C | 15 | 17.0 | 4413 | 2025-04-07 17:01:24 | MASTER-Kislovodsk | (07h 15m 35.87s , +39d 19m 33.6s) | C | 60 | 16.1 | 5084 | 2025-04-07 17:12:35 | MASTER-Kislovodsk | (07h 15m 35.05s , +39d 18m 41.9s) | C | 60 | 15.1 | 18929 | 2025-04-07 21:03:19 | MASTER-Kislovodsk | (07h 24m 40.96s , +39d 08m 54.1s) | C | 60 | 16.1 | 18925 | 2025-04-07 21:03:31 | MASTER-Tunka | (07h 21m 45.98s , +43d 01m 33.5s) | C | 30 | 16.1 | 18955 | 2025-04-07 21:03:31 | MASTER-Tunka | (07h 21m 45.98s , +43d 01m 33.5s) | C | 90 | 16.8 | Coadd 18968 | 2025-04-07 21:04:14 | MASTER-Tunka | (07h 21m 45.94s , +43d 02m 33.2s) | C | 30 | 16.2 | 19010 | 2025-04-07 21:04:56 | MASTER-Tunka | (07h 21m 51.95s , +43d 01m 32.7s) | C | 30 | 16.4 | 19054 | 2025-04-07 21:05:40 | MASTER-Tunka | (07h 21m 47.61s , +43d 00m 31.0s) | C | 30 | 16.5 | 19096 | 2025-04-07 21:06:22 | MASTER-Tunka | (07h 21m 53.31s , +43d 00m 50.5s) | C | 30 | 16.6 | 19139 | 2025-04-07 21:07:05 | MASTER-Tunka | (07h 21m 49.60s , +43d 02m 03.7s) | C | 30 | 16.6 | 19178 | 2025-04-07 21:07:29 | MASTER-Kislovodsk | (07h 27m 46.98s , +41d 04m 05.2s) | C | 60 | 15.7 | 19183 | 2025-04-07 21:07:48 | MASTER-Tunka | (07h 21m 49.75s , +43d 00m 42.4s) | C | 30 | 16.7 | 19213 | 2025-04-07 21:07:48 | MASTER-Tunka | (07h 21m 49.74s , +43d 00m 41.9s) | C | 90 | 17.4 | Coadd 19226 | 2025-04-07 21:08:32 | MASTER-Tunka | (07h 21m 52.80s , +43d 02m 00.8s) | C | 30 | 16.8 | 19268 | 2025-04-07 21:09:14 | MASTER-Tunka | (07h 21m 47.32s , +43d 01m 19.8s) | C | 30 | 16.8 | 19311 | 2025-04-07 21:09:57 | MASTER-Tunka | (07h 21m 46.61s , +43d 02m 19.8s) | C | 30 | 16.7 | 19341 | 2025-04-07 21:09:57 | MASTER-Tunka | (07h 21m 46.59s , +43d 02m 18.6s) | C | 90 | 17.3 | Coadd 19344 | 2025-04-07 21:10:15 | MASTER-Kislovodsk | (07h 20m 26.44s , +42d 57m 56.8s) | C | 60 | 15.8 | 19354 | 2025-04-07 21:10:39 | MASTER-Tunka | (07h 21m 52.13s , +43d 01m 19.1s) | C | 30 | 16.7 | 19398 | 2025-04-07 21:11:23 | MASTER-Tunka | (07h 21m 46.69s , +43d 00m 15.8s) | C | 30 | 16.6 | 19442 | 2025-04-07 21:12:07 | MASTER-Tunka | (07h 28m 37.53s , +42d 02m 35.3s) | C | 30 | 16.3 | 19484 | 2025-04-07 21:12:50 | MASTER-Tunka | (07h 28m 33.74s , +42d 03m 44.2s) | C | 30 | 16.3 | 19527 | 2025-04-07 21:13:32 | MASTER-Tunka | (07h 28m 33.85s , +42d 02m 30.1s) | C | 30 | 16.3 | 19571 | 2025-04-07 21:14:17 | MASTER-Tunka | (07h 28m 36.60s , +42d 03m 41.2s) | C | 30 | 16.2 | 19615 | 2025-04-07 21:15:00 | MASTER-Tunka | (07h 28m 30.97s , +42d 02m 58.7s) | C | 30 | 16.1 | 19659 | 2025-04-07 21:15:45 | MASTER-Tunka | (07h 28m 30.38s , +42d 03m 55.9s) | C | 30 | 16.1 | 19704 | 2025-04-07 21:16:30 | MASTER-Tunka | (07h 21m 53.18s , +43d 00m 59.4s) | C | 30 | 16.2 | 19743 | 2025-04-07 21:17:13 | MASTER-Tunka | (07h 21m 48.54s , +42d 59m 58.8s) | C | 20 | 16.1 | 19774 | 2025-04-07 21:17:45 | MASTER-Tunka | (07h 21m 52.74s , +43d 00m 00.0s) | C | 20 | 16.1 | 19809 | 2025-04-07 21:18:20 | MASTER-Tunka | (07h 21m 50.55s , +43d 01m 39.6s) | C | 20 | 16.2 | 19842 | 2025-04-07 21:18:52 | MASTER-Tunka | (07h 21m 50.60s , +43d 00m 24.5s) | C | 20 | 16.0 | 19875 | 2025-04-07 21:19:25 | MASTER-Tunka | (07h 21m 54.02s , +43d 01m 40.6s) | C | 20 | 15.9 | 19907 | 2025-04-07 21:20:00 | MASTER-Tunka | (07h 21m 47.61s , +43d 00m 52.3s) | C | 15 | 15.8 | 19935 | 2025-04-07 21:20:27 | MASTER-Tunka | (07h 21m 47.97s , +43d 01m 51.2s) | C | 15 | 15.6 | 19964 | 2025-04-07 21:20:57 | MASTER-Tunka | (07h 21m 53.90s , +43d 00m 50.1s) | C | 15 | 15.6 | 19988 | 2025-04-07 21:21:24 | MASTER-Tunka | (07h 21m 47.26s , +42d 59m 49.2s) | C | 10 | 15.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40112. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38135] GRB 250407A: Swift ToO observations
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40111 SUBJECT: GRB 250407A: Swift ToO observations DATE: 25/04/07 20:57:53 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/GBM-detected event GRB 250407A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021826 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/GBM event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40111. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38134] GRB 250407A: SRG/ART-XC afterglow detection
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40110 SUBJECT: GRB 250407A: SRG/ART-XC afterglow detection DATE: 25/04/07 19:48:18 GMT FROM: Sergey Molkov <serge.molkov(a)gmail.com> S. Molkov, A. Tkachenko, I. Mereminskiy, A. Semena, A. Lutovinov, I. Lapshov, V. Arefiev, A. Shtykovskiy and D. Karasev on behalf of the ART-XC team (IKI Moscow) report: During the ongoing all sky survey the Mikhail Pavlinsky ART-XC telescope passed through the localization area of GRB250407A (GCN 40104, GCN 40105) and detected a new X-ray source with coordinates: (RA,Dec)=(110.7564,36.7979) J2000; the 1 sigma statistical error radius is 20 arcsec. The source was in the FoV of the ART-XC telescope during ~20 seconds with a central time of 2025-04-07T17:08:20 UTC (on-board time), approximately 90 minutes after the burst had been detected by GBM (GCN 40104). The mean flux during the transition was about 1.4e-10 ergs/s/cm2 in the 4-12 keV energy band. We expect that it's an afterglow detection of GRB 250407A. Urgent Swift/XRT follow-up observation was requested to obtain precise localization. View this GCN Circular online at https://gcn.nasa.gov/circulars/40110. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38133] LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40109 SUBJECT: LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO DATE: 25/04/07 19:04:57 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> Maia Williams (PSU), Samuele Ronchini (PSU), Gayathri Raman (PSU), James DeLaunay (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU), Aaron Tohuvavohu (Caltech) report: Swift/BAT was observing 100.0% of the GW localization probability ([Bilby.multiorder.fits](https://gracedb.ligo.org/api/superevents/S250331o/fi…) at merger time. A fraction 96.02% of the GW localization posterior is contained inside the BAT coded FoV. The LVK notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; [Tohuvavohu et al. 2020, ApJ, 900, 1](https://iopscience.iop.org/article/10.3847/1538-4357/aba94f)). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. Using the NITRATES analysis ([DeLaunay + Tohuvavohu 2022, ApJ, 941, 169](https://iopscience.iop.org/article/10.3847/1538-4357/ac9d38)), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-7 erg/s/cm^2: |time_bin (s) |soft |normal|hard |GRB170817 |-|-|-|-|-| |0.256 |3.32 |3.49 |3.33 |3.61 |1.024 |1.69 |1.78 |1.70 |1.84 |4.096 |0.91 |0.95 |0.91 |0.99 |16.384 |0.55 |0.58 |0.56 |0.60 The upper limits as function of sky position are plotted here, alongside the GW localization: https://zenodo.org/records/15169889 The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively. The corresponding fits file is also included. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/40109. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38132] IceCube 250406A: DDOTI Optical Observations of the Refined Position
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40108 SUBJECT: IceCube 250406A: DDOTI Optical Observations of the Refined Position DATE: 25/04/07 18:50:45 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), and Margarita Pereyra (UNAM) report: We observed the field of the IceCube 250406A (goldtrack) event (IceCube Collaboration, GCN Circ. 40103) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-07 UTC from 03:12 UTC to 05:19 UTC (from T+4.4 h to T+6.5 h after the trigger) and obtained a total exposure of 1.2 hours. In Becerra et al. (GCN Circ. 40101), we reported a 5-sigma upper limits in the original uncertainty region distributed as a GCN notice (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140752_31006975.amon). Here, we report observations of the updated uncertainty region (IceCube Collaboration, GCN Circ. 40103). In this region, we detect no uncataloged source to a 5-sigma AB limiting magnitude of: w > 20.0 This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40108. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38131] Konus-Wind detection of GRB 250406B (short/hard)
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40107 SUBJECT: Konus-Wind detection of GRB 250406B (short/hard) DATE: 25/04/07 17:14:04 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The bright, short-duration GRB 250406B (IPN localization: Kozyrev et al., GCN 40106). triggered Konus-Wind (KW) at T0=21401.479 s UT (05:56:41.479). The burst light curve shows a multi-peaked pulse, which starts at ~T0-0.032 s and has a duration of ~0.240 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250406_T21401/ As observed by Konus-Wind, the burst had the total fluence of 2.54(-0.51,+0.62)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.016 s, of 3.06(-0.61,+0.69)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.97(-0.10,+0.12) and Ep = 2118(-590,+818) keV (chi2 = 35/38 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -2.15 (chi2 = 35/37 dof). All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40107. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38130] IPN triangulation of GRB 250406B (short/hard)
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40106 SUBJECT: IPN triangulation of GRB 250406B (short/hard) DATE: 25/04/07 17:12:06 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, E. Burns on behalf of the IPN, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The bright, short-duration GRB 250406B was detected by Konus-Wind, Mars-Odyssey (HEND), and Swift (BAT) at about 21400 s UT (05:56:40). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 316.521 (21h 06m 05s) +45.187 (+45d 11' 13") Corners: 317.243 (21h 08m 58s) +45.058 (+45d 03' 28") 315.809 (21h 03m 14s) +45.386 (+45d 23' 10") 315.796 (21h 03m 11s) +45.310 (+45d 18' 36") 317.227 (21h 08m 55s) +44.981 (+44d 58' 53") --------------------------------------------- The error box area is 289 sq. arcmin, and its maximum dimension is 1.078 deg (the minimum one is 4.53 arcmin). The Sun distance was 63 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250406_T21401/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/40106. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38129] GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40105 SUBJECT: GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659) DATE: 25/04/07 16:20:40 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 765733706 at 15:48:21 on 07 April 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 111.6 deg Decl.(2000.0) = 36.5 deg The 1 sigma statistical error radius is 3.5 deg. We estimate an additional systematic error of 2 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250407659/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250407659/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250407659/json View this GCN Circular online at https://gcn.nasa.gov/circulars/40105. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38128] GRB 250407A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40104 SUBJECT: GRB 250407A: Fermi GBM Final Real-time Localization DATE: 25/04/07 15:58:59 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 15:48:21 UT on 7 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250407A (trigger 765733706.065626 / 250407659). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 110.3, Dec = 42.0 (J2000 degrees, equivalent to J2000 07h 21m, 42d 00'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 118.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250407659/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250407659/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250407659/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40104. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38127] EP250404a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40085 SUBJECT: EP250404a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/04/06 09:45:07 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), J. W. Hu (NAO, CAS), Y. L. Hua (PMO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP250404a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hu et al., GCN 40051), and followed up by several telescopes (Jiang et al, GCN 40052, Perez-Garcia et al, GCN 40053, Du et al, GCN 40058, Zhu et al, GCN 40061, Konno et al, GCN 40063, Odeh et al, GCN 40064, Lipunov et al, GCN 40066, He et al, GCN 40069, Pérez-Fournon et al, GCN 40071, Jelinek et al, GCN 40072, Rakotondrainibe et al, GCN 40073, Taguchi et al, GCN 40074, Brivio et al, GCN 40075, Ruocco et al, GCN 70076, Martin-Carrillo et al, GCN 40080, Pavoni et al, GCN 40083, Li et al, GCN 40084), with an optical counterpart detected at a redshift of 2.63 (Zhu et al, GCN 40061, Li et al, GCN 40084). Refined analysis of the WXT data shows that the event started at T0=2025-04-04T14:19:45 (UTC) and lasted for about 16 s before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 0.41 (-0.28/+0.26). The absorption is fixed at the best-fit values from FXT spectral fitting with a Galactic hydrogen column density of 6.00 x 10^20 cm^-2 and an intrinsic hydrogen column density of 4.89 x 10^22 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 5.9 (-1.6/+2.2) x 10^(-8) erg/s/cm^2. The data recovered from the slew process shows that the transient event lasted for about 300 seconds. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 1 min after T0, starting at 2025-04-04T14:20:46 (UTC). Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 125.0601, DEC = 35.5284 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is also consistent with the position of the optical counterpart. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 6.00 x 10^20 cm^-2 and an intrinsic hydrogen column density of 4.89 (-0.45/+0.33) x 10^22 cm^-2. The photon index is 2.18 (-0.03/+0.03). The derived average unabsorbed 0.5-10 keV flux is 9.00 (-0.25/+0.19) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/40085. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38126] IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40103 SUBJECT: IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/04/07 08:06:32 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-04-06 at 22:50:35.34 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for bronze alerts is 50%. This alert has an estimated false alarm rate of 0.9358 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140752_31006975.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-04-06 Time: 22:50:35.34 UT RA: 81.47 (+0.54, -0.53 deg 90% PSF containment) J2000 Dec: 16.96 (+0.42, -0.50 deg 90% PSF containment) J2000 No gamma-ray sources from 4FGL or 3FHL catalogs are in the 90% uncertainty region. We encourage further follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/40103. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38125] IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40102 SUBJECT: IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit DATE: 25/04/07 06:43:32 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Ny Avo Rakotondrainibe (LAM), Noémie Globus (UNAM), Jean-Grégoire Ducoin (CPPM), Kin Ocelotl López (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We observed the field of the IceCube 250406.951 (goldtrack) event with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-07 UTC. COLIBRÍ tiled the IceCube error region from 03:09 UTC to 04:18 UTC (from T+4.3 h to T+5.5 h after the trigger) with a total exposure of 47 minutes. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025). Comparing our observations (and after performing image subtraction) against Pan-STARRS DR2, we detect no evident uncatalogued sources within the observed field to a 5-sigma limiting AB magnitude of: i > 22.2 This non-detection is consistent with the reported by Becerra et al., GCN 40101. This value is not corrected for the Galactic extinction. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40102. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38124] IceCube 250406.951: DDOTI Optical Observations
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40101 SUBJECT: IceCube 250406.951: DDOTI Optical Observations DATE: 25/04/07 06:03:17 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of the IceCube 250406.951 (goldtrack) event with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-07 UTC. DDOTI observed the IceCube error region from 03:12 UTC to 03:40 UTC (from T+4.4 h to T+4.8 h after the trigger) with a total exposure of 24 minutes. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues and after performed image subtraction against PanSTARRS PS1 DR2, we detect no evident uncatalogued sources within the observed field to a 5-sigma limiting AB magnitude of w > 19.7 This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40101. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38123] GRB 250406A: AstroSat CZTI detection
by GCN Circulars 07 Apr '25

07 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40100 SUBJECT: GRB 250406A: AstroSat CZTI detection DATE: 25/04/07 04:27:16 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 250406A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40094). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-06 14:38:19.0 UTC. The measured peak count rate associated with the burst is 126 (+25, -17) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1195 (+285, -117) counts. The local mean background count rate was 226 (+1, -6) counts/s. Using cumulative rates, we measure a T90 of 17 (+4, -2) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-06 14:38:17.9 UTC. The measured peak count rate associated with the burst is 329 (+70, -44) counts/s above the background in the combined data of all quadrants, with a total of 2697 (+493, -543) counts. The local mean background count rate was 1320 (+7, -8) counts/s. We measure a T90 of 16 (+5, -5) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40100. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38122] IceCube Alert 250406.95: Global MASTER-Net observations report
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40099 SUBJECT: IceCube Alert 250406.95: Global MASTER-Net observations report DATE: 25/04/06 23:39:44 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the IceCube Alert 250406.95 (trigger No 31006975,05h 27m 14.40s , +16d 40m 08.4s, R=0.51) errorbox 1665 sec after notice time and 1717 sec after trigger time at 2025-04-06 23:19:12 UT, with upper limit up to 19.3 mag. Observations started at twilight. The observations began at zenith distance = 57 deg. The sun altitude is -12.5 deg. The galactic latitude b = -9 deg., longitude l = 189 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2835304 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1798 | 2025-04-06 23:19:12 | MASTER-OAFA | (05h 36m 30.18s , +17d 17m 13.8s) | C | 160 | 15.5 | 1984 | 2025-04-06 23:22:18 | MASTER-OAFA | (05h 36m 29.96s , +17d 17m 16.2s) | C | 160 | 16.3 | 2144 | 2025-04-06 23:22:18 | MASTER-OAFA | (05h 36m 29.96s , +17d 17m 16.2s) | C | 480 | 16.9 | Coadd 2170 | 2025-04-06 23:25:24 | MASTER-OAFA | (05h 36m 29.72s , +17d 17m 19.0s) | C | 160 | 16.5 | 2180 | 2025-04-06 23:25:25 | MASTER-OAFA | (05h 27m 00.20s , +16d 54m 03.9s) | C | 180 | 15.6 | 2356 | 2025-04-06 23:28:31 | MASTER-OAFA | (05h 36m 29.47s , +17d 17m 21.0s) | C | 160 | 16.8 | 2366 | 2025-04-06 23:28:31 | MASTER-OAFA | (05h 27m 00.08s , +16d 54m 05.7s) | C | 180 | 19.1 | 2542 | 2025-04-06 23:31:37 | MASTER-OAFA | (05h 36m 29.25s , +17d 17m 22.1s) | C | 160 | 16.6 | 2552 | 2025-04-06 23:31:37 | MASTER-OAFA | (05h 26m 59.99s , +16d 54m 07.1s) | C | 180 | 19.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40099. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38121] Fermi trigger No 765663719: Global MASTER-Net observations report
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40098 SUBJECT: Fermi trigger No 765663719: Global MASTER-Net observations report DATE: 25/04/06 20:46:19 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB250406.85 (trigger No 765663719,19h 59m 09.60s , +36d 07m 12.0s, R=7.99) errorbox 216 sec after notice time and 235 sec after trigger time at 2025-04-06 20:25:49 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 40 deg. The sun altitude is -18.6 deg. The galactic latitude b = 3 deg., longitude l = 73 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2835171 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 265 | 2025-04-06 20:25:49 | MASTER-Tunka | (19h 43m 55.63s , +35d 11m 35.6s) | C | 60 | 17.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40098. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38120] EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40097 SUBJECT: EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14 DATE: 25/04/06 19:33:24 GMT FROM: qiang xi <xiqiang051(a)gmail.com> Qiang-Xi (UCAS), Yiming-Mao (NAOC), Xinxiang-Sun (NAOC), Ningchen-Sun (NAOC), Junjie-Jin (NAOC), Min-He (NAOC) report: We detected an optical counterpart for the field of EP 250404A using two independent facilities: the 70 cm telescope UCAS-70 and the 35 cm telescope XL-C14. The optical counterpart was observed at the coordinates: **RA = 08h20m14.54s, Dec = +35°31′42.2″.** Stacked imaging of the field has revealed a clear optical transient. The photometric measurements derived from the stacked images are summarized below. In our analysis, the photometry in the Johnson band was calibrated from APASS data converted using the Lupton (2005) equations, while the SDSS band data were calibrated against the SDSS star catalog. The observation time reported corresponds to the median of the individual exposure times. | Median Time (UT) | Telescope | Exposure (s) | Filter | Magnitude | Err | | ----------------------- | --------- | ------------ | ------ | ---------------- | ---- | | 2025-04-04 15:42:35.500 | UCAS-70 | 6×180 | B | 18.73 | 0.24 | | 2025-04-04 15:45:44.199 | UCAS-70 | 6×180 | V | 17.89 | 0.12 | | 2025-04-04 15:48:52.780 | UCAS-70 | 6×180 | R | 17.18 | 0.14 | | 2025-04-04 15:52:01.952 | UCAS-70 | 6×180 | I | 16.76 | 0.13 | | 2025-04-04 16:04:43.721 | XL-C14 | 11×120 | g | <22.10( 3-sigma limit) | | | 2025-04-04 16:17:19.682 | XL-C14 | 13×120 | r | 17.59 | 0.19 | | 2025-04-04 16:15:12.716 | XL-C14 | 13×120 | i | 17.15 | 0.20 | | 2025-04-04 15:58:22.729 | XL-C14 | 8×120 | z | <17.41( 3-sigma limit) | | This measurement has not been corrected for galaxy extinction. Our observations are consistent with other already reported Jiang et al. (GCN 40052), Perez-Garcia et al. (GCN 40053), Du et al. (GCN 40058), Zhu et al. (GCN 40061), Konno et al. (GCN 40063), Odeh et al. (GCN 40064), Lipunov et al. (GCN 40066), Min-He et al. (GCN 40069), Lipunov et al. (GCN 40070), Perez-Fournon et al. (GCN 40071), Jelinek et al. (GCN 40072), Rakotondrainibe et al. (GCN 40073), Taguchi et al. (GCN 40074), Brivio et al. (GCN 40075), Ruocco (GCN 40076), Martin-Carrillo et al. (GCN 40080), Pavoni et al. (GCN 40083), Li et al. (GCN 40084), Yin et al. (GCN 40085), Pankov et al. (GCN 40086), Chen et al. (GCN 40088), Chen et al. (GCN 40089), Pankov et al. (GCN 40090), Leonini et al. (GCN 40093), Leonini et al(GCN40095). View this GCN Circular online at https://gcn.nasa.gov/circulars/40097. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38119] Fermi GRB 250406A: Global MASTER-Net observations report
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40096 SUBJECT: Fermi GRB 250406A: Global MASTER-Net observations report DATE: 25/04/06 18:15:59 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250406A ( Fermi GBM team, GCN 40094) errorbox 9143 sec after notice time and 9171 sec after trigger time at 2025-04-06 17:11:03 UT, with upper limit up to 18.1 mag. Observations started at twilight. The observations began at zenith distance = 68 deg. The sun altitude is -9.9 deg. The galactic latitude b = -54 deg., longitude l = 308 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2834949 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9202 | 2025-04-06 17:11:03 | MASTER-SAAO | (00h 25m 46.55s , -63d 33m 50.2s) | C | 60 | 16.6 | 9281 | 2025-04-06 17:12:22 | MASTER-SAAO | (00h 43m 35.96s , -63d 32m 39.4s) | C | 60 | 16.8 | 9360 | 2025-04-06 17:13:41 | MASTER-SAAO | (00h 24m 01.48s , -61d 38m 12.8s) | C | 60 | 16.8 | 9439 | 2025-04-06 17:15:01 | MASTER-SAAO | (00h 40m 43.37s , -61d 39m 07.2s) | C | 60 | 17.0 | 9519 | 2025-04-06 17:16:20 | MASTER-SAAO | (00h 27m 48.66s , -65d 26m 57.7s) | C | 60 | 17.2 | 9803 | 2025-04-06 17:21:04 | MASTER-SAAO | (00h 09m 41.55s , -63d 33m 51.5s) | C | 60 | 17.6 | 9889 | 2025-04-06 17:22:30 | MASTER-SAAO | (00h 25m 49.55s , -63d 32m 19.4s) | C | 60 | 17.7 | 10129 | 2025-04-06 17:26:30 | MASTER-SAAO | (00h 43m 41.72s , -63d 33m 01.9s) | C | 60 | 17.9 | 10209 | 2025-04-06 17:27:50 | MASTER-SAAO | (00h 23m 59.75s , -61d 39m 57.8s) | C | 60 | 17.7 | 10289 | 2025-04-06 17:29:10 | MASTER-SAAO | (00h 40m 51.41s , -61d 39m 35.0s) | C | 60 | 17.9 | 10368 | 2025-04-06 17:30:29 | MASTER-SAAO | (00h 27m 50.49s , -65d 25m 58.4s) | C | 60 | 17.8 | 10653 | 2025-04-06 17:35:14 | MASTER-SAAO | (00h 09m 43.11s , -63d 32m 50.4s) | C | 60 | 18.0 | 10733 | 2025-04-06 17:36:34 | MASTER-SAAO | (00h 25m 48.42s , -63d 31m 49.8s) | C | 60 | 17.9 | 10812 | 2025-04-06 17:37:53 | MASTER-SAAO | (00h 43m 45.24s , -63d 32m 51.2s) | C | 60 | 18.1 | 10892 | 2025-04-06 17:39:13 | MASTER-SAAO | (00h 24m 03.87s , -61d 39m 50.1s) | C | 60 | 17.9 | 10971 | 2025-04-06 17:40:32 | MASTER-SAAO | (00h 40m 54.53s , -61d 39m 38.8s) | C | 60 | 17.8 | 11051 | 2025-04-06 17:41:52 | MASTER-SAAO | (00h 27m 55.06s , -65d 25m 49.8s) | C | 60 | 17.8 | 11335 | 2025-04-06 17:46:36 | MASTER-SAAO | (00h 09m 48.00s , -63d 32m 47.3s) | C | 60 | 17.8 | 11415 | 2025-04-06 17:47:56 | MASTER-SAAO | (00h 25m 51.70s , -63d 31m 45.0s) | C | 60 | 17.9 | 11494 | 2025-04-06 17:49:15 | MASTER-SAAO | (00h 43m 49.94s , -63d 32m 44.3s) | C | 60 | 17.9 | 11574 | 2025-04-06 17:50:35 | MASTER-SAAO | (00h 24m 06.65s , -61d 39m 45.5s) | C | 60 | 17.9 | 11653 | 2025-04-06 17:51:54 | MASTER-SAAO | (00h 40m 58.05s , -61d 39m 30.5s) | C | 60 | 17.9 | 12144 | 2025-04-06 18:00:05 | MASTER-SAAO | (00h 28m 06.48s , -65d 25m 50.6s) | C | 60 | 17.9 | 12430 | 2025-04-06 18:04:52 | MASTER-SAAO | (00h 10m 03.09s , -63d 32m 45.1s) | C | 60 | 17.8 | 12510 | 2025-04-06 18:06:11 | MASTER-SAAO | (00h 25m 59.78s , -63d 33m 39.9s) | C | 60 | 17.8 | 12589 | 2025-04-06 18:07:30 | MASTER-SAAO | (00h 43m 57.06s , -63d 33m 07.7s) | C | 60 | 17.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40096. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38118] GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40095 SUBJECT: GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations. DATE: 25/04/06 17:44:24 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250404A detected by Fermi Gamma-ray Burst Monitor (GBM team, GCN 40050) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-04-04 22:45 UT (approximately 8.42 hours after burst) stacking a set of unfiltered CCD image. The observations were made with modest visibility conditions: passing clouds and Moon (illumin. 48%, dist. 19°) The OT was detected at the following position (+/- 0.3 arcsec): RA (J2000.0) 08h 20m 14.59s Decl. (J2000.0) +35° 31' 41.5" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-04 23:27:00 UT 9.12 82x60s CR 20.16 +/-0.2 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Jiang et al. (GCN 40052), Perez-Garcia et al. (GCN 40053), Du et al. (GCN 40058), Zhu et al. (GCN 40061), Konno et al. (GCN 40063), Odeh et al. (GCN 40064), Lipunov et al. (GCN 40066), Min-He et al. (GCN 40069), Lipunov et al. (GCN 40070), Perez-Fournon et al. (GCN 40071), Jelinek et al. (GCN 40072), Rakotondrainibe et al. (GCN 40073), Taguchi et al. (GCN 40074), Brivio et al. (GCN 40075), Ruocco (GCN 40076), Martin-Carrillo et al. (GCN 40080), Pavoni et al. (GCN 40083), Li et al. (GCN 40084), Yin et al. (GCN 40085), Pankov et al. (GCN 40086), Chen et al. (GCN 40088), Chen et al. (GCN 40089), Pankov et al. (GCN 40090), Leonini et al. (GCN 40093). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40095. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38117] GRB 250406A: Fermi GBM Final Real-time Localization
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40094 SUBJECT: GRB 250406A: Fermi GBM Final Real-time Localization DATE: 25/04/06 14:48:42 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 14:38:11 UT on 6 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250406A (trigger 765643096.56557 / 250406610). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 6.2, Dec = -63.2 (J2000 degrees, equivalent to J2000 00h 24m, -63d 12'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 29.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40094. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38116] EP250404a / GRB 250404A: Montarrenti Observatory optical observations
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40093 SUBJECT: EP250404a / GRB 250404A: Montarrenti Observatory optical observations DATE: 25/04/06 13:49:11 GMT FROM: Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini(a)iol.it> S. Leonini, A. Lorini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: we observed the field of the X-ray transient EP250404a (Einstein Probe mission, Trigger ID 01709133918) probably associated with GRB 250404A (Fermi team, GCN 40050) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88). The observations were started at 2025-04-04 18:36:04 UT (approximately 4 hours after burst) ending at 2025-04-04 22:00:50 UT stacking a set of Rc-band CCD images. Observations were performed under thin cloud cover in the second part of the night. The optical afterglow (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al, GCN 40064; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al, GCN 40073; Taguchi et al., GCN 40074; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085; Pankov et al., GCN 40086; Chu Chen et al., GCN 40088 and Chen et al., GCN 40089) was clearly detected at the following position: RA (J2000.0) 08h 20m 14.57s +/-0.06 Decl. (J2000.0) +35° 31' 42.0" +/-0.04 Preliminary photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-04 18:36:24 UT 4.27 50x40s Rc 19.60 +/-0.10 2025-04-04 19:11:30 UT 4.85 50x40s Rc 19.67 +/-0.10 2025-04-04 19:46:31 UT 5.43 50x40s Rc 19.81 +/-0.15 2025-04-04 20:21:33 UT 6.02 54x40s Rc 20.25 +/-0.20 2025-04-04 21:07:10 UT 6.78 78x40s Rc 20.16 +/-0.12 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Along the span of our observations and within our uncertainties, the afterglow evolves in agreement with a power-law decay with a rate alpha ~1.40. View this GCN Circular online at https://gcn.nasa.gov/circulars/40093. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38115] Fermi trigger No 765619921: Global MASTER-Net observations report
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40092 SUBJECT: Fermi trigger No 765619921: Global MASTER-Net observations report DATE: 25/04/06 13:46:45 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250406.34 (trigger No 765619921,16h 27m 07.92s , +59d 07m 01.2s, R=50) errorbox 915 sec after notice time and 949 sec after trigger time at 2025-04-06 08:27:46 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 49 deg. The sun altitude is -30.9 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB250406.34 errorbox 18661 sec after notice time and 18696 sec after trigger time at 2025-04-06 13:23:33 UT, with upper limit up to 18.3 mag. Observations started at twilight. The observations began at zenith distance = 73 deg. The sun altitude is -14.9 deg. The galactic latitude b = 41 deg., longitude l = 89 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2834649 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 970 | 2025-04-06 08:27:46 | MASTER-OAFA | (15h 28m 20.65s , +13d 16m 46.0s) | C | 40 | 18.2 | 980 | 2025-04-06 08:27:46 | MASTER-OAFA | (15h 19m 00.28s , +12d 54m 07.9s) | C | 60 | 20.0 | 2262 | 2025-04-06 08:49:18 | MASTER-OAFA | (15h 28m 22.19s , +13d 17m 10.6s) | C | 40 | 18.3 | 2272 | 2025-04-06 08:49:18 | MASTER-OAFA | (15h 19m 02.07s , +12d 54m 31.6s) | C | 60 | 20.0 | 3654 | 2025-04-06 09:12:30 | MASTER-OAFA | (15h 28m 15.85s , +13d 17m 06.0s) | C | 40 | 18.3 | 3665 | 2025-04-06 09:12:31 | MASTER-OAFA | (15h 18m 56.28s , +12d 54m 26.8s) | C | 60 | 20.0 | 5045 | 2025-04-06 09:35:41 | MASTER-OAFA | (15h 28m 20.02s , +13d 18m 20.6s) | C | 40 | 18.2 | 5055 | 2025-04-06 09:35:41 | MASTER-OAFA | (15h 19m 00.70s , +12d 55m 40.3s) | C | 60 | 20.0 | 18727 | 2025-04-06 13:23:33 | MASTER-Tunka | (18h 23m 55.12s , +49d 33m 54.6s) | C | 60 | 18.2 | 18995 | 2025-04-06 13:28:01 | MASTER-Tunka | (18h 23m 53.09s , +49d 33m 24.0s) | C | 60 | 18.0 | 19206 | 2025-04-06 13:31:32 | MASTER-Tunka | (18h 23m 50.27s , +49d 34m 17.4s) | C | 60 | 18.2 | 19597 | 2025-04-06 13:38:03 | MASTER-Tunka | (18h 23m 50.38s , +49d 32m 59.3s) | C | 60 | 18.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40092. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38114] Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40091 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB DATE: 25/04/06 13:13:13 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca(a)unitn.it> A. Holzmann Airasca (UniTrento and INFN Bari) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 765619921/250406342 at 08:11:56.54 UT on 06 April 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to an accidental trigger." View this GCN Circular online at https://gcn.nasa.gov/circulars/40091. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38113] GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40090 SUBJECT: GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit DATE: 25/04/06 13:05:06 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE), A.N. Tarasenkov (INASAN), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed GRB 250404A / EP250404a (Fermi GBM team, GCN 40050; Hu et al., GCN 40051; Frederiks et al., GCN 40087) with RC500 telescope of the INASAN-Kislovodsk observatory. The optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085; Pankov et al., GCN 40086; Chen et al., GCN 40088;) is not detected starting on 2025-04-04 (UT) 21:10:11. Preliminary upper limit of the stacked image is the following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2025-04-04 21:10:11 0.33362 R 70*120 n/d n/d 20.1 The photometry is based on nearby USNO-B1.0 stars. View this GCN Circular online at https://gcn.nasa.gov/circulars/40090. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38112] GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40089 SUBJECT: GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations DATE: 25/04/06 12:27:20 GMT FROM: Chen Liang-Jun at Guangxi University <chenlj(a)st.gxu.edu.cn> L. J. Chen(GXU), L. P. Xin(NAOC), Y. G. Yang(HNU), X. H. Han, C. WU, Y. L. Qiu, J. Wang, H. L. Li, X .M. Lu, R. S. Zhang, Y. Xu, L. Huang, H. B. Cai, Y. J. Xiao, P. P. Zhang, L. Lan, W. J. Xie, Z. H. Yao, J. Y. Wei(NAOC), X. G. Wang, E. W. Liang(GXU) report on behalf of the SVOM follow-up team: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050), with the GWAC-F50A and GWAC-F60 at Xinglong Observatory, China. F50 started observing at 2025-04-04T14:25:34 UTC and lasted until 2025-04-04T15:36:36 with 9 frames in R-band and 15 frames in I-band. F60A started observing at 2025-04-04T14:24:56 UTC and lasted until 2025-04-04T15:24:21 with 25 frames in R-band. F60B started observing at 2025-04-04T14:25:05 UTC and lasted until 2025-04-04T15:24:28 with 25 frames in R-band. The optical counterpart of GRB 250404A / EP250404a (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Pankov et al., GCN 40086), was clearly detected in our images. The afterglow shows a first brightening and then a single decay with a peak magnitude of R~14.3 mag, calibrated to the USNO B1.0 catalog, at about 1000 sec after the burst. Two 60cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 19*19 arcmin. The 50cm telescope (F50A) is operated by Huaibei Normal University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 27*27 arcmin. View this GCN Circular online at https://gcn.nasa.gov/circulars/40089. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38111] EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40088 SUBJECT: EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope DATE: 25/04/06 12:26:24 GMT FROM: Chun Chen at Sun Yat-sen University, SYSU 80cm telescope team <chench386(a)mail2.sysu.edu.cn> Chun Chen, Xia Li, Zhong-Nan Dong, Jia-Qi Lin, Wei-Sen Huang, Jin-Ji Li, Pu Lin, Hao-Nan Yang, Yan Yu, Hao-Ran Zhang, Hao-Yuan Zheng, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm telescope team: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB250404A (Fermi GBM team, GCN40050; Fermi GBM team, GCN40067), using the Sun Yat-sen University 80cm infrared telescope with 183 x 20 s exposures in J band. The calculated position is R.A. = 125.0575 deg, DEC = 35.5305 deg J2000, from EP/FXT observation. Our observations began at 2025-4-4 15:25:20 UTC, 1.09 hours after the EP trigger. We detected a counterpart at the position of the optical afterglow (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al. GCN 40063; Odeh et al., GCN 40064; Lipunov et al., GCN 40066; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Ruocco, GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084) in the stacked images. The preliminary photometric magnitudes in J band are below: Start Time (UTC) |Band | Exp | Mag (Vega) --------------------|-----|-------|------------------ 2025/4/4 15:25:20 | J | 200s | 15.30+/-0.08 2025/4/4 15:28:40 | J | 200s | 15.28+/-0.09 2025/4/4 15:32:20 | J | 200s | 15.47+/-0.10 2025/4/4 15:35:40 | J | 200s | 15.76+/-0.11 2025/4/4 15:39:00 | J | 360s | 15.83+/-0.10 2025/4/4 15:50:20 | J | 400s | 16.05+/-0.12 2025/4/4 15:57:00 | J | 400s | 15.99+/-0.12 2025/4/4 16:03:40 | J | 400s | 15.99+/-0.12 2025/4/4 16:10:40 | J | 400s | 16.29+/-0.15 2025/4/4 16:17:40 | J | 1100s | 16.21+/-0.11 The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitudes are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40088. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38110] Konus-Wind detection of GRB 250404A / EP250404a
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40087 SUBJECT: Konus-Wind detection of GRB 250404A / EP250404a DATE: 25/04/06 12:08:53 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250404A (Fermi-GBM detection: The Fermi GBM team, GCN 40050; Mukherjee & Meegan, GCN 40067), coincident with the X-ray transient EP250404a (Hu et al., GCN 40051), triggered Konus-Wind (KW) at T0=51605.773 s UT (14:20:05.773). The burst light curve shows a multi-peaked structure which starts at ~T0-21 s and has a total duration of ~105 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250404_T51605/ As observed by Konus-Wind, the burst had a fluence of (2.83 ± 0.09)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.832 s, of (1.78 ± 0.22)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+81.186 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.38(-0.13,+0.14) and Ep = 56(-5,+4) keV (chi2 = 76/98 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -3.5 (chi2 = 76/97 dof). The spectrum near the peak count rate(measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a CPL with alpha = -1.16(-0.17,+0.19) and Ep = 68(-9,+8) keV (chi2 = 90/96 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -4.2 (chi2 = 90/95 dof). Assuming the redshift z ~ 2.627 ( Li et al., GCN 40084) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (4.60 ± 0.14)x10^53 erg, the isotropic peak luminosity L_iso to (1.05 ± 0.13)x10^53 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z to (203 ± 18) keV, and the rest-frame peak energy at the peak of the emission Ep,p,z to (247 ± 30) keV. With the obtained estimates, GRB 250404A lies at the lower edge, but is consistent with 90% prediction bands of the 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250404_T51605/GRB250404A_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40087. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38109] GRB 250404A / EP250404a: Mondy optical observations
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40086 SUBJECT: GRB 250404A / EP250404a: Mondy optical observations DATE: 25/04/06 11:27:55 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed GRB 250404A / EP250404a (Fermi GBM team, GCN 40050; Hu et al., GCN 40051). The optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085) is early detected on 2025-04-04 and was observed between (UT) 14:50:52 and 17:09:01. We obtained an upper limit on 2025-04-05. Preliminary photometry of some stacked images is the following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2025-04-04 14:50:52 0.04244 R 40*90 16.53 0.02 22.4 2025-04-04 16:01:21 0.08999 R 28*120 17.96 0.03 22.2 2025-04-05 15:08:33 1.05611 R 42*90 n/d n/d 21.5 The photometry is based on nearby USNO-B1.0 stars. View this GCN Circular online at https://gcn.nasa.gov/circulars/40086. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38108] EP250404a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40085 SUBJECT: EP250404a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/04/06 09:45:07 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), J. W. Hu (NAO, CAS), Y. L. Hua (PMO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP250404a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hu et al., GCN 40051), and followed up by several telescopes (Jiang et al, GCN 40052, Perez-Garcia et al, GCN 40053, Du et al, GCN 40058, Zhu et al, GCN 40061, Konno et al, GCN 40063, Odeh et al, GCN 40064, Lipunov et al, GCN 40066, He et al, GCN 40069, Pérez-Fournon et al, GCN 40071, Jelinek et al, GCN 40072, Rakotondrainibe et al, GCN 40073, Taguchi et al, GCN 40074, Brivio et al, GCN 40075, Ruocco et al, GCN 70076, Martin-Carrillo et al, GCN 40080, Pavoni et al, GCN 40083, Li et al, GCN 40084), with an optical counterpart detected at a redshift of 2.63 (Zhu et al, GCN 40061, Li et al, GCN 40084). Refined analysis of the WXT data shows that the event started at T0=2025-04-04T14:19:45 (UTC) and lasted for about 16 s before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 0.41 (-0.28/+0.26). The absorption is fixed at the best-fit values from FXT spectral fitting with a Galactic hydrogen column density of 6.00 x 10^20 cm^-2 and an intrinsic hydrogen column density of 4.89 x 10^22 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 5.9 (-1.6/+2.2) x 10^(-8) erg/s/cm^2. The data recovered from the slew process shows that the transient event lasted for about 300 seconds. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 1 min after T0, starting at 2025-04-04T14:20:46 (UTC). Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 125.0601, DEC = -35.5284 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is also consistent with the position of the optical counterpart. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 6.00 x 10^20 cm^-2 and an intrinsic hydrogen column density of 4.89 (-0.45/+0.33) x 10^22 cm^-2. The photon index is 2.18 (-0.03/+0.03). The derived average unabsorbed 0.5-10 keV flux is 9.00 (-0.25/+0.19) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/40085. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38107] GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
by GCN Circulars 06 Apr '25

06 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40084 SUBJECT: GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627 DATE: 25/04/06 03:57:18 GMT FROM: Rui-Zhi Li at Yunnan Observatories, CAS <liruizhi(a)ynao.ac.cn> R.-Z. Li, B.-T. Wang, F.-F. Song, J. Mao, H.-C. Feng and J.-M. Bai (YNAO, CAS) report: GRB 250404A / EP250404a was detected by Fermi GBM (Fermi GBM team, GCN 40050) and by EP/WXT (Hu et al., GCN 40051). We observed the optical counterpart of GRB 250404A / EP250404a (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083). The spectroscopic observation was conducted using the GMG-2.4m telescope with Grism #14, which provides a wavelength coverage of 3600–7460 AA. A single 1800s spectrum was obtained, with exposure beginning at 2025-04-04T15:18:24, about 0.98 hours after the Fermi/GBM and EP/WXT trigger (Fermi GBM team, GCN 40050; Hu et al., GCN 40051). Two absorption systems were identified in the spectrum. For the first absorption system, we detected multiple metal absorption features, including Si II at 1527 AA, Al II at 1671 AA, Al III at 1855 AA and 1863 AA, Zn II/Cr II at 2026 AA and 2062 AA, and Fe II at 2344 AA, 2374 AA, and 2383 AA. These features consistently indicate a redshift of z ~ 1.881. For the second absorption system, the spectrum shows multiple metal absorption lines from Si II/S II at 1260 AA, O I/Si II at 1303 AA, C II at 1335 AA, Si IV at 1394 AA, Si II at 1527 AA, Fe II at 1608 AA, and Al III at 1863 AA. These absorption features correspond to a redshift of z ~ 2.627. These results support a redshift of z ~ 2.627 for the transient, consistent with the measurement reported by Xinglong-2.16m (Zhu et al., GCN 40061). We thank the staff at the Lijiang Observatory for their support in conducting the observation. View this GCN Circular online at https://gcn.nasa.gov/circulars/40084. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38106] GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40083 SUBJECT: GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection DATE: 25/04/05 22:56:51 GMT FROM: leavittob(a)gmail.com E. Pavoni, L. Moretti (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050), with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Manciano, Italy. Median moon illumination of 47% was present. The observations started approximately 5.1 hours after the trigger time, stacking a series of R-Cousins filtered exposures, for a total integration time of approximately 88 minutes. All images were processed using the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). We detected the optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al. GCN 40063; Odeh et al., GCN 40064; Lipunov et al., GCN 40066; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Ruocco, GCN 40076; Martin-Carrillo et al., GCN 40080) in the stacked image at the following coordinates +/- 2 arcsec: R.A. (J2000) = 08:20:14:59 Dec. (J2000) = +35:31:41:75 with the following photometry: Date UT at mid-exposure: 2025-04-04 20:24:18 UTC Mag (R Cousins) 19.47 Error +/- 0.2 Magnitudes were estimated with the Pan-STARRS cat. and converted using Lupton (2005) equations. No corrected for galactic dust extinction. The message may be cited. Reference: https://leavittobservatory.altervista.org View this GCN Circular online at https://gcn.nasa.gov/circulars/40083. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38105] GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40082 SUBJECT: GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations. DATE: 25/04/05 22:22:30 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250402A (SVOM burst-id sb25040203, Chen et al., GCN 40014) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-04-02 23:57 UT (approximately 49 min after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and fair visibility conditions. The OT was detected at the following position (+/- 0.3 arcsec): RA (J2000.0) 14h 13m 38.17s Decl. (J2000.0) -05° 55' 48.8" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-03 01:39:02 UT 2.52 180x60s CR 21.6 +/- 0.4 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported L.P. Xin et al. (GCN 40015), Pérez-Fournon et al. (GCN 40020), Brivio et al. (GCN 40021), Schneider et al. (GCN 40022), Magnani et al. (GCN 40023), Komesh et al. (GCN 40033), Shilling et al. (GCN 40047), Mazaeva et al. (GCN 40049). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40082. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38104] EP250402a: Optical upper limit with PD 1.3m observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40081 SUBJECT: EP250402a: Optical upper limit with PD 1.3m observations DATE: 25/04/05 17:05:25 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> Jonathan Quirola-Vásquez (Radboud), Peter G. Jonker (Radboud), Franz Bauer (PUC), Antonio Martin-Carrillo (UCD), Andrew J. Levan (Radboud), Daniele B. Malesani (DAWN/ NBI and Radboud), Javi Sánchez-Sierras (Radboud), Agnes van Hoof (Radboud), Jennifer Chacon (PUC), Joyce van Dalen (Radboud) report on behalf of a larger collaboration: We obtained photometric observations of the field of the fast X-ray transient EP250402a discovered by Einstein Probe (Li et al., GCN 40017, GCN 40038) using the Planaetry Defense 1.3m telescope localized in Cerro Tololo Inter-American Observatory, Chile. We obtained 30 images of 120 s each in the r-band filter beginning at 2025-04-03 07:06:41 UT and with a middle time at T0+0.797 days after the EP trigger. Within the EP-FXT error circle, we detect no plausible optical counterpart down to a 3sigma limit of r > 21.8 AB mag, calibrated against SkyMapper nearby reference stars We acknowledge the excellent support from the PD 1.3m staff, in particular Tyler Linder. View this GCN Circular online at https://gcn.nasa.gov/circulars/40081. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38103] GRB 250404A / EP250404a: NOT optical observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40080 SUBJECT: GRB 250404A / EP250404a: NOT optical observations DATE: 25/04/05 15:27:15 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo (UCD), B. Schneider (LAM), A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. An (NAOC), D. Xu (NAOC), G. Corcoran (UCD), Dimple (U. Birmingham), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration: We observed the field of EP250404a (Hu et al., GCN 40051), likely associated with GRB 250404A detected by Fermi/GBM (Fermi GBM team, GCN 40050; Mukherjee & Meegan, GCN 40067) using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained exposures in the SDSS-r (3x180 s) and SDSS-z (2x180 s) bands, starting at 22:09:17 UT on 2025-04-04 (7.82 hr after the EP trigger). The optical counterpart reported by Jiang et al. (GCN. 40052), Perez-Garcia et al. (GCN 40053), Du et al. (GCN 40058), Zhu et al. (GCN 40061), Konno et al. (GCN 40063), Odeh et al. (GCN 40064), He et al. (GCN 40069), Pérez-Fournon et al. (GCN 40071), Jelinek et al. (GCN 40072), Rakotondrainibe et al. (GCN 40073), Taguchi et al. (GCN 40074), Ruocco et al. (GCN 40076) is well detected in the stacked images, with the following preliminary magnitudes: r = 20.43 +/- 0.05 (7.90 hr after trigger); z = 19.79 +/- 0.06 (8.04 hr after trigger). The photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40080. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38102] GRB 250331D: Swift-XRT afterglow detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40079 SUBJECT: GRB 250331D: Swift-XRT afterglow detection DATE: 25/04/05 12:24:26 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the Swift/BAT-detected burst GRB 250331D. The observations now extend from T0+45.3 ks to T0+406.9 ks and have a total exposure time of 8.6 ks. Of the sources previously reported, "Source 2" is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 3064 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 48.65718, +62.28326 which is equivalent to: RA (J2000): 03h 14m 37.72s Dec(J2000): +62d 16' 59.8" with an uncertainty of 3.5 arcsec (radius, 90% confidence). This position is 3.9 arcmin from the Swift/BAT position. There is evidence that the source may be fading, however we cannot constrain the decay at the current time. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021825/Source2.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021825. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40079. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38101] GRB 250404B: AstroSat CZTI detection of a short burst
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40078 SUBJECT: GRB 250404B: AstroSat CZTI detection of a short burst DATE: 25/04/05 10:39:48 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> S. Salunke (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short duration GRB 250404B. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-04-04 18:36:09.15 UTC. The measured peak count rate associated with the burst is 720 (+181, -101) counts/s above the background in the combined data of three quadrants (out of four), with a total of 375 (+52, -54) counts. The local mean background count rate was 292 (+10, -13) counts/s. Using cumulative rates, we measure a T90 of 0.79 (+0.04, -0.05) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaked at 2025-04-04 18:36:08.40 UTC. The measured peak count rate associated with the burst is 665 (+73, -81) counts/s above the background in the combined data of all quadrants, with a total of 635 (+154, -167) counts. The local mean background count rate was 1266 (+14, -15) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40078. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38100] GRB 250403A: AstroSat CZTI detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40077 SUBJECT: GRB 250403A: AstroSat CZTI detection DATE: 25/04/05 10:38:20 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 250403A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 40025) and SVOM/ECLAIRs (Y. Julakanti et. al. GCN Circ. 40026). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-03 15:15:26.00 UTC. The measured peak count rate associated with the burst is 80 (+18, -23) counts/s above the background in the combined data of three quadrants (out of four), with a total of 343 (+110, -184) counts. The local mean background count rate was 225 (+3, -2) counts/s. Using cumulative rates, we measure a T90 of 9.1 (+1.3, -5.5) s. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40077. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38099] EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40076 SUBJECT: EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart DATE: 25/04/05 10:05:39 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission triggered EP-WXT (ID: 01709133918) (GCN Circular 40051 J. W. Hu (NAO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. L. Hua (PMO, CAS), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team), I pointed at the coordinates RA(J2000)= 08:20:14.59 : Dec(J2000)= +35:31:42.3 and started observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Clear sky but moon presence at about 20 degrees from the target. The observations started at 20:36 UT of 2025/04/04, after about 6 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME I took 22 unfiltered images of 120 sec . Start End Rlim 20:36:23 UT 21:22:15 UT 20.5 All images, calibrated with masterdark and masterflat have been measured with Thycho Tracker software We have detected a faint source at the enhanced position reported by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission AT following position RA (J2000.0) 08 20 15.95 Dec (J2000.0) +35 31 48.3 with the following photometry and astrometry: EP250404a 08 20 15.95 +35 31 48.3 19.0 C82 Magnitudes were estimated with the ATLAS cat. and are not corrected for galactic dust extinction. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40076. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38098] EP250404a: REM optical/NIR observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40075 SUBJECT: EP250404a: REM optical/NIR observations DATE: 25/04/05 09:32:41 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of EP250404a (Hu et al., GCN 40051), likely associated with GRB 250404A detected by Fermi/GBM (Fermi GBM team, GCN 40050) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 April 04 at 23:26:12 UT (i.e. 9.1 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (Jiang et al., GCN. 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074) down to the following 3sigma limits: r > 19.7 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 9.6 hours after the trigger; H > 16.3 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 9.5 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40075. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38097] EP250404a: Seimei/TriCCS optical counterpart detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40074 SUBJECT: EP250404a: Seimei/TriCCS optical counterpart detection DATE: 25/04/05 09:09:53 GMT FROM: Kenta Taguchi <kentagch(a)kusastro.kyoto-u.ac.jp> Kenta Taguchi, Keiichi Maeda (Kyoto U.), Masaomi Tanaka (Tohoku U.) report on behalf of a larger collaboration: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051) using the Tricolor CMOS Camera and Spectrograph (TriCCS) on the 3.8-m Seimei telescope. Observations started at 15:27:48 UT on 2025-04-04 (MJD = 60769.64). We detected a counterpart at a position consistent with the source detected by Jiang et al. (GCN 40052, also reported by Perez-Garcia et al. GCN 40053, Du et al. GCN 40058, Konno et al. GCN 40063, Odeh et al. GCN 40064, He et al. GCN 40069, Pérez-Fournon et al. GCN 40071, Jelinek et al. GCN 40072, Rakotondrainibe et al. GCN 40073). Preliminary analysis gives the following magnitudes of the source: g = 18.20 +- 0.05 r = 17.46 +- 0.04 i = 17.10 +- 0.03 View this GCN Circular online at https://gcn.nasa.gov/circulars/40074. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38096] EP250404A: COLIBRÍ/DDRAGO Optical Observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40073 SUBJECT: EP250404A: COLIBRÍ/DDRAGO Optical Observations DATE: 25/04/05 08:31:34 GMT FROM: Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe(a)gmail.com> Ny Avo Rakotondrainibe (LAM), Jean-Grégoire Ducoin (CPPM), Rosa L. Becerra (U Roma), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Sarah Antier (OCA/IJCLAB), Stéphane Basa (UAR Pytheas), Diego López-Cámara (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Ramandeep Gill (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Antonio de Ugarte Postigo (LAM) and Benjamin Schneider (LAM) report: We imaged the field of EP250404A (Hu et al., GCN Circ. 40051) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-05 UTC. We observed from 2025-04-05 05:39 to 06:18 UTC (T+15.3 to T+16.0 hours after the trigger) and obtained 1920 seconds of exposure in total in the r filter. Our observations were performed under regular weather conditions. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. We detected the optical counterpart (Jiang et al., GCN Circ. 40052, Perez-Garcia et al., GCN Circ. 40053, Du et al., GCN Circ. 40058, Zhu et al., GCN Circ. 40061, Konno et al. GCN Circ. 40063, Odeh et al., GCN Circ. 40064, Lipunov et al., GCN Circ. 40066, He et al., GCN Circ. 40069, Perez-Fournon et al., GCN Circ. 40071, Jelinek et al., GCN Circ. 40072) with an AB magnitude of: r = 21.99 +/- 0.15. Compared with the values previously reported, we estimate the fading nature of the OT with a temporal index ~1.4 after T+1.7 hours. Further observations and analysis are ongoing. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40073. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38095] EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40072 SUBJECT: EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection DATE: 25/04/05 03:49:34 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny, R. Hudec (ASU CAS Ondrejov) report:We observed the field of EP250404a detected by EP (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050; Mukherjee et al., GCN 40067), using the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. Our observations started at 15:50 UT on 2025-04-04, approximately 5.5 hours after the trigger. We performed a series of 120s exposures in the SDSS i' filter. The optical counterpart, previously reported by several teams (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071), is detected in our combined image of 25x120s exposures. The PanSTARRS-calibrated magnitude of the source is i' = 19.5 +/- 0.1, not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40072. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38094] EP250404a: LCO optical counterpart detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40071 SUBJECT: EP250404a: LCO optical counterpart detection DATE: 25/04/05 00:52:37 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), D. Aguado, A. López-Oramas, D. Nespral (IAC and ULL), N.C. Sun (UCAS), W. Li, Y. Wang, and Z. Niu (NAOC) We report on Las Cumbres Observatory Global Telescope network (LCOGT) observations of the X-ray transient EP250404a (Hu et al., GCN circ. 40051), that is temporally and spatially consistent with the likely long GRB 250404A, detected by Fermi/GBM (Fermi GBM team, GCN 40050; and Mukherjee et al., GCN circ. 40067). We observed the field of EP250404a with the two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Observatory (Tenerife, Spain) in the SDSS i, g, and r filters, starting at 2025-04-04 20:27:26 UTC, about 6.12 hours after the EP trigger. An uncatalogued source is clearly detected in the three images at the position of the optical counterpart first reported by Jiang et al. (GCN circ. 40052) and also detected by Perez-Garcia et al. (GCN circ. 40053), Du et al. (GCN circ. 40058), Zhu et al. (GCN circ. 40061), Konno et al. (GCN circ. 40063), Odeh et al. (GCN circ. 40064), and He et al. (GCN circ. 40069). A redshift of z = 2.63 has been reported by Zhu et al. (GCN circ. 40061). We measure the following preliminary magnitudes, calibrated against Pan-STARRS DR2 stars, that are not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-04-04 20:27:26 20.11 0.22 i 300 2025-04-04 22:01:01 20.65 0.16 g 300 2025-04-04 22:05:55 20.38 0.11 r 300 This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40071. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38093] Fermi GRB 250404A: Global MASTER-Net observations report
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40070 SUBJECT: Fermi GRB 250404A: Global MASTER-Net observations report DATE: 25/04/05 00:17:01 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250404A ( Fermi GBM team, GCN 40050) errorbox 16599 sec after notice time and 16639 sec after trigger time at 2025-04-04 18:57:05 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 66 deg. The sun altitude is -28.6 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250404A errorbox 31880 sec after notice time and 31919 sec after trigger time at 2025-04-04 23:11:46 UT, with upper limit up to 19.3 mag. Observations started at twilight. The observations began at zenith distance = 67 deg. The sun altitude is -10.4 deg. The galactic latitude b = 32 deg., longitude l = 188 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2832903 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16669 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 60 | 18.6 | 16729 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 180 | 19.3 | Coadd 16740 | 2025-04-04 18:58:16 | MASTER-Tunka | (08h 19m 58.07s , +36d 00m 34.7s) | C | 60 | 18.6 | 16812 | 2025-04-04 18:59:28 | MASTER-Tunka | (08h 19m 55.11s , +36d 02m 04.0s) | C | 60 | 18.6 | 16885 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 60 | 18.7 | 16945 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 180 | 19.4 | Coadd 16962 | 2025-04-04 19:01:58 | MASTER-Tunka | (08h 19m 57.66s , +36d 02m 04.7s) | C | 60 | 18.6 | 17033 | 2025-04-04 19:03:09 | MASTER-Tunka | (08h 19m 52.37s , +36d 01m 15.7s) | C | 60 | 18.7 | 17108 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.7s) | C | 60 | 18.7 | 17168 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.8s) | C | 180 | 19.5 | Coadd 17393 | 2025-04-04 19:09:09 | MASTER-Tunka | (08h 19m 52.28s , +35d 59m 59.8s) | C | 60 | 18.7 | 17466 | 2025-04-04 19:10:22 | MASTER-Tunka | (08h 19m 58.20s , +36d 00m 10.2s) | C | 60 | 18.7 | 17540 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.3s) | C | 60 | 18.7 | 17600 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.2s) | C | 180 | 19.4 | Coadd 17612 | 2025-04-04 19:12:48 | MASTER-Tunka | (08h 19m 54.27s , +35d 59m 56.4s) | C | 60 | 18.6 | 17683 | 2025-04-04 19:13:59 | MASTER-Tunka | (08h 19m 57.20s , +36d 01m 34.1s) | C | 60 | 18.6 | 17756 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 60 | 18.5 | 17816 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 180 | 19.3 | Coadd 17829 | 2025-04-04 19:16:24 | MASTER-Tunka | (08h 19m 51.76s , +36d 01m 37.4s) | C | 60 | 18.6 | 17903 | 2025-04-04 19:17:39 | MASTER-Tunka | (08h 19m 57.64s , +36d 00m 34.5s) | C | 60 | 18.7 | 17975 | 2025-04-04 19:18:51 | MASTER-Tunka | (08h 19m 51.82s , +35d 59m 30.3s) | C | 60 | 18.6 | 18035 | 2025-04-04 19:18:51 | MASTER-Tunka | (08h 19m 51.82s , +35d 59m 30.3s) | C | 180 | 19.4 | Coadd 18048 | 2025-04-04 19:20:04 | MASTER-Tunka | (08h 19m 57.26s , +35d 59m 42.1s) | C | 60 | 18.6 | 18120 | 2025-04-04 19:21:16 | MASTER-Tunka | (08h 19m 53.77s , +36d 01m 07.0s) | C | 60 | 18.5 | 18192 | 2025-04-04 19:22:28 | MASTER-Tunka | (08h 19m 53.78s , +35d 59m 24.2s) | C | 60 | 18.6 | 18252 | 2025-04-04 19:22:28 | MASTER-Tunka | (08h 19m 53.78s , +35d 59m 24.1s) | C | 180 | 19.4 | Coadd 18263 | 2025-04-04 19:23:39 | MASTER-Tunka | (08h 19m 57.55s , +36d 00m 59.3s) | C | 60 | 18.7 | 18337 | 2025-04-04 19:24:53 | MASTER-Tunka | (08h 19m 50.49s , +36d 00m 11.6s) | C | 60 | 18.6 | 31925 | 2025-04-04 23:11:46 | MASTER-OAFA | (08h 08m 19.47s , +34d 59m 12.3s) | C | 10 | 14.9 | 31925 | 2025-04-04 23:11:46 | MASTER-OAFA | (08h 19m 21.81s , +35d 21m 51.8s) | C | 10 | 16.5 | 31967 | 2025-04-04 23:12:28 | MASTER-OAFA | (08h 08m 15.18s , +35d 00m 30.7s) | C | 10 | 14.9 | 31967 | 2025-04-04 23:12:28 | MASTER-OAFA | (08h 19m 17.72s , +35d 23m 08.7s) | C | 10 | 16.6 | 32005 | 2025-04-04 23:13:06 | MASTER-OAFA | (08h 08m 15.01s , +34d 58m 38.5s) | C | 10 | 14.9 | 32005 | 2025-04-04 23:13:06 | MASTER-OAFA | (08h 19m 17.32s , +35d 21m 15.2s) | C | 10 | 16.7 | 32044 | 2025-04-04 23:13:45 | MASTER-OAFA | (08h 08m 17.35s , +35d 00m 09.4s) | C | 10 | 15.1 | 32044 | 2025-04-04 23:13:45 | MASTER-OAFA | (08h 19m 19.90s , +35d 22m 45.2s) | C | 10 | 16.8 | 32086 | 2025-04-04 23:14:27 | MASTER-OAFA | (08h 08m 10.02s , +34d 59m 29.2s) | C | 10 | 15.2 | 32086 | 2025-04-04 23:14:27 | MASTER-OAFA | (08h 19m 12.52s , +35d 22m 04.1s) | C | 10 | 16.8 | 32127 | 2025-04-04 23:15:08 | MASTER-OAFA | (08h 08m 11.16s , +35d 00m 25.4s) | C | 10 | 15.2 | 32127 | 2025-04-04 23:15:08 | MASTER-OAFA | (08h 19m 13.83s , +35d 22m 59.5s) | C | 10 | 16.8 | 32165 | 2025-04-04 23:15:45 | MASTER-OAFA | (08h 08m 16.58s , +34d 59m 22.6s) | C | 10 | 15.3 | 32165 | 2025-04-04 23:15:46 | MASTER-OAFA | (08h 19m 19.15s , +35d 21m 56.2s) | C | 10 | 17.0 | 32204 | 2025-04-04 23:16:24 | MASTER-OAFA | (08h 08m 09.70s , +34d 58m 17.6s) | C | 10 | 15.3 | 32204 | 2025-04-04 23:16:25 | MASTER-OAFA | (08h 19m 12.12s , +35d 20m 50.5s) | C | 10 | 16.9 | 32241 | 2025-04-04 23:17:02 | MASTER-OAFA | (08h 08m 15.41s , +34d 58m 44.1s) | C | 10 | 15.3 | 32241 | 2025-04-04 23:17:02 | MASTER-OAFA | (08h 19m 17.91s , +35d 21m 16.7s) | C | 10 | 17.0 | 32280 | 2025-04-04 23:17:41 | MASTER-OAFA | (08h 08m 11.54s , +35d 00m 01.8s) | C | 10 | 15.3 | 32280 | 2025-04-04 23:17:41 | MASTER-OAFA | (08h 19m 14.23s , +35d 22m 33.8s) | C | 10 | 17.0 | 32318 | 2025-04-04 23:18:19 | MASTER-OAFA | (08h 08m 11.34s , +34d 58m 27.0s) | C | 10 | 15.3 | 32318 | 2025-04-04 23:18:19 | MASTER-OAFA | (08h 19m 13.81s , +35d 20m 58.4s) | C | 10 | 17.1 | 32356 | 2025-04-04 23:18:57 | MASTER-OAFA | (08h 08m 13.99s , +34d 59m 41.3s) | C | 10 | 15.4 | 32357 | 2025-04-04 23:18:57 | MASTER-OAFA | (08h 19m 16.67s , +35d 22m 12.7s) | C | 10 | 17.2 | 33140 | 2025-04-04 23:32:01 | MASTER-OAFA | (08h 07m 59.46s , +34d 58m 26.5s) | C | 10 | 15.7 | 33150 | 2025-04-04 23:32:01 | MASTER-OAFA | (08h 19m 01.71s , +35d 21m 07.7s) | C | 30 | 18.4 | 33186 | 2025-04-04 23:32:47 | MASTER-OAFA | (08h 07m 58.57s , +34d 59m 30.7s) | C | 10 | 15.8 | 33197 | 2025-04-04 23:32:47 | MASTER-OAFA | (08h 19m 01.06s , +35d 22m 10.1s) | C | 30 | 18.4 | 33235 | 2025-04-04 23:33:35 | MASTER-OAFA | (08h 08m 03.56s , +34d 58m 34.6s) | C | 10 | 15.8 | 33245 | 2025-04-04 23:33:36 | MASTER-OAFA | (08h 19m 05.95s , +35d 21m 12.1s) | C | 30 | 18.5 | 33280 | 2025-04-04 23:34:21 | MASTER-OAFA | (08h 07m 56.35s , +34d 57m 37.5s) | C | 10 | 15.8 | 33290 | 2025-04-04 23:34:21 | MASTER-OAFA | (08h 18m 58.65s , +35d 20m 14.0s) | C | 30 | 18.4 | 33328 | 2025-04-04 23:35:09 | MASTER-OAFA | (08h 08m 02.36s , +34d 58m 09.7s) | C | 10 | 15.9 | 33338 | 2025-04-04 23:35:09 | MASTER-OAFA | (08h 19m 04.81s , +35d 20m 45.1s) | C | 30 | 18.6 | 33373 | 2025-04-04 23:35:54 | MASTER-OAFA | (08h 07m 58.28s , +34d 59m 32.8s) | C | 10 | 15.8 | 33384 | 2025-04-04 23:35:54 | MASTER-OAFA | (08h 19m 00.96s , +35d 22m 07.7s) | C | 30 | 18.5 | 33424 | 2025-04-04 23:36:45 | MASTER-OAFA | (08h 07m 57.86s , +34d 58m 00.1s) | C | 10 | 15.8 | 33434 | 2025-04-04 23:36:45 | MASTER-OAFA | (08h 19m 00.34s , +35d 20m 33.9s) | C | 30 | 18.5 | 33464 | 2025-04-04 23:36:45 | MASTER-OAFA | (08h 19m 00.33s , +35d 20m 33.8s) | C | 90 | 19.3 | Coadd 33471 | 2025-04-04 23:37:32 | MASTER-OAFA | (08h 08m 01.00s , +34d 59m 22.3s) | C | 10 | 15.8 | 33481 | 2025-04-04 23:37:32 | MASTER-OAFA | (08h 19m 03.70s , +35d 21m 55.5s) | C | 30 | 18.5 | 33519 | 2025-04-04 23:38:20 | MASTER-OAFA | (08h 07m 54.12s , +34d 58m 51.0s) | C | 10 | 15.9 | 33529 | 2025-04-04 23:38:20 | MASTER-OAFA | (08h 18m 56.76s , +35d 21m 23.8s) | C | 30 | 18.5 | 33566 | 2025-04-04 23:39:07 | MASTER-OAFA | (08h 07m 52.92s , +34d 59m 53.3s) | C | 10 | 15.9 | 33576 | 2025-04-04 23:39:07 | MASTER-OAFA | (08h 18m 55.71s , +35d 22m 25.5s) | C | 30 | 18.5 | 33606 | 2025-04-04 23:39:07 | MASTER-OAFA | (08h 18m 55.72s , +35d 22m 25.5s) | C | 90 | 19.3 | Coadd 33613 | 2025-04-04 23:39:54 | MASTER-OAFA | (08h 07m 58.66s , +34d 58m 55.1s) | C | 10 | 15.9 | 33624 | 2025-04-04 23:39:54 | MASTER-OAFA | (08h 19m 01.35s , +35d 21m 27.0s) | C | 30 | 18.5 | 33659 | 2025-04-04 23:40:40 | MASTER-OAFA | (08h 07m 51.06s , +34d 57m 56.5s) | C | 10 | 15.9 | 33669 | 2025-04-04 23:40:40 | MASTER-OAFA | (08h 18m 53.65s , +35d 20m 28.1s) | C | 30 | 18.4 | 33721 | 2025-04-04 23:41:27 | MASTER-OAFA | (08h 07m 56.45s , +34d 58m 08.6s) | C | 40 | 16.6 | 33731 | 2025-04-04 23:41:27 | MASTER-OAFA | (08h 18m 59.04s , +35d 20m 38.8s) | C | 60 | 18.4 | 33799 | 2025-04-04 23:42:45 | MASTER-OAFA | (08h 07m 52.46s , +34d 59m 53.5s) | C | 40 | 16.6 | 33809 | 2025-04-04 23:42:45 | MASTER-OAFA | (08h 18m 55.24s , +35d 22m 22.0s) | C | 60 | 18.6 | 33874 | 2025-04-04 23:44:00 | MASTER-OAFA | (08h 07m 51.72s , +34d 58m 08.4s) | C | 40 | 16.5 | 33885 | 2025-04-04 23:44:00 | MASTER-OAFA | (08h 18m 54.29s , +35d 20m 36.9s) | C | 60 | 18.6 | 33950 | 2025-04-04 23:45:16 | MASTER-OAFA | (08h 07m 52.58s , +34d 59m 42.2s) | C | 40 | 16.6 | 33961 | 2025-04-04 23:45:16 | MASTER-OAFA | (08h 18m 55.38s , +35d 22m 10.2s) | C | 60 | 18.6 | 34029 | 2025-04-04 23:46:35 | MASTER-OAFA | (08h 07m 46.04s , +34d 59m 09.7s) | C | 40 | 16.5 | 34039 | 2025-04-04 23:46:35 | MASTER-OAFA | (08h 18m 48.79s , +35d 21m 37.5s) | C | 60 | 18.6 | 34105 | 2025-04-04 23:47:51 | MASTER-OAFA | (08h 07m 44.23s , +35d 00m 11.7s) | C | 40 | 16.6 | 34116 | 2025-04-04 23:47:51 | MASTER-OAFA | (08h 18m 47.13s , +35d 22m 39.2s) | C | 60 | 18.6 | 34183 | 2025-04-04 23:49:09 | MASTER-OAFA | (08h 07m 50.81s , +34d 59m 13.6s) | C | 40 | 16.6 | 34193 | 2025-04-04 23:49:09 | MASTER-OAFA | (08h 18m 53.60s , +35d 21m 41.4s) | C | 60 | 18.6 | 34258 | 2025-04-04 23:50:24 | MASTER-OAFA | (08h 07m 43.46s , +34d 58m 15.9s) | C | 40 | 16.7 | 34268 | 2025-04-04 23:50:24 | MASTER-OAFA | (08h 18m 46.23s , +35d 20m 43.3s) | C | 60 | 18.9 | 34334 | 2025-04-04 23:51:40 | MASTER-OAFA | (08h 07m 49.53s , +34d 58m 37.1s) | C | 40 | 16.7 | 34344 | 2025-04-04 23:51:40 | MASTER-OAFA | (08h 18m 52.40s , +35d 21m 04.5s) | C | 60 | 19.0 | 34412 | 2025-04-04 23:52:58 | MASTER-OAFA | (08h 07m 45.63s , +34d 59m 52.0s) | C | 40 | 16.7 | 34422 | 2025-04-04 23:52:58 | MASTER-OAFA | (08h 18m 48.68s , +35d 22m 19.3s) | C | 60 | 19.0 | 34490 | 2025-04-04 23:54:16 | MASTER-OAFA | (08h 07m 45.61s , +34d 58m 24.1s) | C | 40 | 16.7 | 34500 | 2025-04-04 23:54:16 | MASTER-OAFA | (08h 18m 48.48s , +35d 20m 51.3s) | C | 60 | 19.0 | 34568 | 2025-04-04 23:55:34 | MASTER-OAFA | (08h 07m 47.51s , +34d 59m 56.5s) | C | 40 | 16.7 | 34578 | 2025-04-04 23:55:34 | MASTER-OAFA | (08h 18m 50.62s , +35d 22m 23.7s) | C | 60 | 19.0 | 34694 | 2025-04-04 23:57:00 | MASTER-OAFA | (08h 18m 44.27s , +35d 21m 54.2s) | C | 120 | 19.3 | 34823 | 2025-04-04 23:59:19 | MASTER-OAFA | (08h 07m 41.05s , +35d 00m 30.6s) | C | 100 | 16.9 | 34833 | 2025-04-04 23:59:19 | MASTER-OAFA | (08h 18m 44.29s , +35d 22m 57.6s) | C | 120 | 19.3 | 34970 | 2025-04-05 00:01:46 | MASTER-OAFA | (08h 07m 46.89s , +34d 59m 33.9s) | C | 100 | 17.1 | 34981 | 2025-04-05 00:01:46 | MASTER-OAFA | (08h 18m 50.01s , +35d 22m 01.1s) | C | 120 | 19.3 | 35095 | 2025-04-05 00:04:06 | MASTER-OAFA | (08h 07m 41.46s , +34d 58m 36.8s) | C | 70 | 16.9 | 35105 | 2025-04-05 00:04:06 | MASTER-OAFA | (08h 18m 44.44s , +35d 21m 04.0s) | C | 90 | 19.1 | 35202 | 2025-04-05 00:05:53 | MASTER-OAFA | (08h 07m 45.68s , +34d 58m 59.5s) | C | 70 | 17.0 | 35212 | 2025-04-05 00:05:53 | MASTER-OAFA | (08h 18m 48.74s , +35d 21m 26.6s) | C | 90 | 19.1 | 35308 | 2025-04-05 00:07:39 | MASTER-OAFA | (08h 07m 42.99s , +35d 00m 18.1s) | C | 70 | 16.9 | 35319 | 2025-04-05 00:07:39 | MASTER-OAFA | (08h 18m 46.22s , +35d 22m 44.9s) | C | 90 | 19.1 | 35398 | 2025-04-05 00:09:24 | MASTER-OAFA | (08h 07m 42.93s , +34d 59m 00.1s) | C | 40 | 16.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40070. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38092] EP250404a: Xinglong decaying optical counterpart
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40069 SUBJECT: EP250404a: Xinglong decaying optical counterpart DATE: 25/04/04 22:17:12 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Min-He (NAOC), Yiming-Mao (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Jinlei-Zhang (NAOC), Junjun-Jia (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report: We observed the field of the X-ray transient, EP 250404a, detected by EP/WXT using the Xinglong 0.8-m, 2.16-m telescope located at Xinglong, Hebei, China. We obtained 6 x 300 s g'-band frames for 0.8-m telescope, 5 * 300s clear-band frames for 2.16-m telescope during the time between 2025-04-04T14:32:21.91 and 2025-04-04T17:08:42 as soon as the EP trigger. We have found the optical counterpart of EP 250404a in these images, and the light of this object had been decreased rapidly. The magnitude of this object firstly be ~ 15.68+/- 0.014 at 2025-04-04T14:32:21.91 with 0.8-m telescope in g'-band, and then decrease to ~ 19.7+/-0.102 with 2.16-m telescope at a median time of 2025-04-04T17:03:42, which measured by a stacked clear-band image and calibrated with the Pan-STARRS r' band field. The stacked clear-band image using the 2.16-m telescope has a 5-sigma limiting magnitude of ~21.64 mag, calibrated with the Pan-STARRS r'-band field. Within the 20 arcsec error circle of the FXT, we identified an optical transient (OT) localized at R. A. = 08:20:11.41 , Dec. = 35:31:27.68 (J2000). We summarize our observation results as follows: Obs. No. | Start Time (UTC) | End Time (UTC) | Exposure Time (s) | Filter | Apparent mag (AB) |Telescope Name 1 | 2025-04-04 14:32:21.91 | 2025-04-04 14:37:21.91 | 300s | g' | 15.681 +/- 0.014 | Xinglong 0.8-m Telescope. 2 | 2025-04-04 14:37:27.81 | 2025-04-04 14:42:27.81 | 300s | g' | 15.717 +/- 0.013 | Xinglong 0.8-m Telescope. 3 | 2025-04-04 14:42:33.76 | 2025-04-04 14:47:33.76 | 300s | g' | 16.124 +/- 0.019 | Xinglong 0.8-m Telescope. 4 | 2025-04-04 15:11:06.35 | 2025-04-04 15:16:06.35 | 300s | g' | 17.864 +/- 0.070 | Xinglong 0.8-m Telescope. 5 | 2025-04-04 15:16:12.26 | 2025-04-04 15:21:12.26 | 300s | g' | 18.149 +/- 0.088 | Xinglong 0.8-m Telescope. 6 | 2025-04-04 15:21:18.16 | 2025-04-04 15:26:18.16 | 300s | g' | 19.015 +/- 0.112 | Xinglong 0.8-m Telescope. 7 | 2025-04-04 14:37:24 | 2025-04-04 14:42:24 | 300s |clear| 14.882 +/- 0.001 (calibrated to r') | Xinglong 2.16-m Telescope. 8 | 2025-04-04 14:42:32 | 2025-04-04 14:47:32 | 300s |clear| 15.363 +/- 0.002 (calibrated to r')| Xinglong 2.16-m Telescope. 9 | 2025-04-04 16:58:22 | 2025-04-04 17:13:42 | 3x300s |clear| 19.703 +/- 0.102 (calibrated to r')| Xinglong 2.16-m Telescope Further observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/40069. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38091] GRB 250403A: Montarrenti Observatory optical detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40068 SUBJECT: GRB 250403A: Montarrenti Observatory optical detection DATE: 25/04/04 21:35:28 GMT FROM: Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini(a)iol.it> S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: we observed the field of GRB 250403A detected by Fermi/GBM (Fermi team, GCN 40025), SVOM/ECLAIRs (Julakanti et al., GCN 40026) and SWIFT (Dichiara et al., GCN 40037; Shilling et al., GCN 40048) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88). The observations were started at 2025-04-03 21:56:50 UT (approximately 7 hours after burst) stacking a set of Rc-band CCD images. The elevation of the field decreased from 19 degrees above the horizon. The optical afterglow (Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032; Julakanti et al., GCN 40034; Ghosh et al, GCN 40039; Jiang et al., GCN 40041; Perez-Fournon et al., GCN 40043; Brivio et al., GCN 40044; Xin et al, GCN 40045 and Zheng et al., GCN 40065) was barely detected (S/N=2.4) at the following position: RA (J2000.0) 12h 58m 27.72s +/-0.15 Decl. (J2000.0) -24° 22' 46.5" +/-0.19 Preliminary photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. UL (3-sigma) 2025-04-03 21:57:10 UT 6.68 94x40s Rc 20.10 S/N =2.4 >19.90 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. View this GCN Circular online at https://gcn.nasa.gov/circulars/40068. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38090] GRB 250404A: Fermi GBM Detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40067 SUBJECT: GRB 250404A: Fermi GBM Detection DATE: 25/04/04 19:52:20 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:19:46.35 UT on 04 April 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250404A (trigger 765469191/250404597). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 123.37, Dec = 34.10 (J2000 degrees, equivalent to J2000 8h 13m, +34d 6'), with a statistical uncertainty of 1.20 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 42 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 91.4 s (50-300 keV). The time-averaged spectrum from T0-3.6 to T0+124.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.10 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 55.7 +/- 0.5 keV. The event fluence (10-1000 keV) in this time interval is (3.33 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+21 s in the 10-1000 keV band is 12.9 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40067. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38089] EP250404a: Global MASTER-Net observations report
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40066 SUBJECT: EP250404a: Global MASTER-Net observations report DATE: 25/04/04 19:27:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP250404a ( EP Team et al., GCN 40051) errorbox 13675 sec after notice time and 16626 sec after trigger time at 2025-04-04 18:57:05 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 66 deg. The sun altitude is -28.6 deg. The galactic latitude b = 33 deg., longitude l = 187 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2832935 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16657 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 60 | 18.6 | 16717 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 180 | 19.3 | Coadd 16728 | 2025-04-04 18:58:16 | MASTER-Tunka | (08h 19m 58.07s , +36d 00m 34.7s) | C | 60 | 18.6 | 16800 | 2025-04-04 18:59:28 | MASTER-Tunka | (08h 19m 55.11s , +36d 02m 04.0s) | C | 60 | 18.6 | 16872 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 60 | 18.7 | 16932 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 180 | 19.4 | Coadd 16950 | 2025-04-04 19:01:58 | MASTER-Tunka | (08h 19m 57.66s , +36d 02m 04.7s) | C | 60 | 18.6 | 17021 | 2025-04-04 19:03:09 | MASTER-Tunka | (08h 19m 52.37s , +36d 01m 15.7s) | C | 60 | 18.7 | 17095 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.7s) | C | 60 | 18.7 | 17155 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.8s) | C | 180 | 19.5 | Coadd 17381 | 2025-04-04 19:09:09 | MASTER-Tunka | (08h 19m 52.28s , +35d 59m 59.8s) | C | 60 | 18.7 | 17454 | 2025-04-04 19:10:22 | MASTER-Tunka | (08h 19m 58.20s , +36d 00m 10.2s) | C | 60 | 18.7 | 17527 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.3s) | C | 60 | 18.7 | 17587 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.2s) | C | 180 | 19.4 | Coadd 17599 | 2025-04-04 19:12:48 | MASTER-Tunka | (08h 19m 54.27s , +35d 59m 56.4s) | C | 60 | 18.6 | 17670 | 2025-04-04 19:13:59 | MASTER-Tunka | (08h 19m 57.20s , +36d 01m 34.1s) | C | 60 | 18.6 | 17743 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 60 | 18.5 | 17803 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 180 | 19.3 | Coadd 17816 | 2025-04-04 19:16:24 | MASTER-Tunka | (08h 19m 51.76s , +36d 01m 37.4s) | C | 60 | 18.6 | 17890 | 2025-04-04 19:17:39 | MASTER-Tunka | (08h 19m 57.64s , +36d 00m 34.5s) | C | 60 | 18.7 | 17962 | 2025-04-04 19:18:51 | MASTER-Tunka | (08h 19m 51.82s , +35d 59m 30.3s) | C | 60 | 18.6 | 18035 | 2025-04-04 19:20:04 | MASTER-Tunka | (08h 19m 57.26s , +35d 59m 42.1s) | C | 60 | 18.6 | 18108 | 2025-04-04 19:21:16 | MASTER-Tunka | (08h 19m 53.77s , +36d 01m 07.0s) | C | 60 | 18.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40066. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38088] GRB 250403A: KAIT optical observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40065 SUBJECT: GRB 250403A: KAIT optical observations DATE: 25/04/04 18:53:09 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 250403A (Julakanti et al., GCN 40026; Fermi GBM team, GCN 40025) with a set of 120x60s images in the clear (roughly R) filters, at a mid time of 16.0 hours after the trigger. We marginally detected the optical afterglow (Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032, Julakanti et al., GCN 40034; Ghosh et al., GCN 40039; Jiang et al., GCN 40041; Pérez-Fournon et al., GCN 40043; Brivio et al., GCN 40044; Xin et al., GCN Circ. 40045) in the coadd image with a brightness of 21.2 +/- 0.4 mag (Vega). View this GCN Circular online at https://gcn.nasa.gov/circulars/40065. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38087] EP250404a: AKO Optical Afterglow Detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40064 SUBJECT: EP250404a: AKO Optical Afterglow Detection DATE: 25/04/04 18:35:28 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 <mshodeh(a)gmail.com> Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of EP250404a detected by EP (Hu et al., GCN 40051), using our 0.36m f/7.7 robotic telescope. The observation session began on 04 April 2025 at 15:47 UT and continued until 16:56 UT, with a midpoint at 16:22 UT, approximately 2 hours after the trigger. We obtained multiple 180-second exposures using the Ic filter. The optical afterglow was clearly detected at: R.A. (J2000): 08:20:14.59 Dec. (J2000): +35:31:42.3 Our detection is consistent with the results of (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Konno et al., GCN 40063). The following observation was calculated using the Atlas catalogue as a reference: ---------------------------------------------------------------------------- - ObsTime (mid), Exposure (sec), Filter, Mag ---------------------------------------------------------------------------- - 2025-04-04T16:21:38Z, 20 x 180s (stacked), Ic, 17.5 +/- 0.35 ---------------------------------------------------------------------------- - The magnitude is not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40064. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38086] EP250404a: LAST detection of optical counterpart
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40063 SUBJECT: EP250404a: LAST detection of optical counterpart DATE: 25/04/04 18:17:33 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslan.konno(a)desy.de> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), P. Chen (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), S. Spitzer (WIS), and K. Rybicki (WIS) on behalf of the LAST Collaboration We report observations of the X-ray transient EP250404a (Hu et al., GCN 40051), detected by Einstein Probe, with the Large Array Survey Telescope (LAST; Ofek et al. 2023 PASP 135, 5001; Ben-Ami et al. 2023 PASP 135, 5002). We observe the field of EP250404a using 4 parallel telescopes, each with a FoV of 7.4 deg^2 and no filter (clear - similar to the GAIA Bp band) over several epochs. In each epoch, we coadd 20 images with each of 20s exposure, and the limiting magnitude of a single coadd is around 20.5 (AB mag). We clearly detect the optical counterpart reported by Jiang et al. (GCN 40052), Perez-Garcia et al. (GCN 40053), and Du et al. (GCN 40058). The earliest detection with a 20x20s exposure image is confirmed at 2025-04-04 17:01:04 UTC (T-T0=2.68h) at an AB magnitude of 19.31 +/- 0.07. LAST is scheduled to continue observations of the source, and additional analysis will follow. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/). View this GCN Circular online at https://gcn.nasa.gov/circulars/40063. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38085] GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40062 SUBJECT: GRB 250402A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/04/04 18:11:36 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250402A onboard (T0: 2025-04-02T23:08:01.467 UTC, SVOM trig sb25040203, Fermi trig 765328094) The Fermi and SVOM notices, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 8.2 in a 4.096 s analysis time bin, starting at T0 + 7.168 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 5,905 deg2 and the 50% credible area is 1,632 deg2. The integrated probability inside the coded field of view is 1%. The NITRATES skymap is consistent with the SVOM/ECLAIRS position (GCN 40014), and the afterglow position (SVOM/VT GCN 40015, SVOM/MXT GCN 40019, LCO GCN 40020, SVOM/COLIBRI GCN 40023, Swift/XRT GCN 40027, EP/FXT GCN 40040, Mondy GCN 40049) A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=765328116/#:~:te… The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/765328116/0_n_PROBMAP) Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=765328116 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/40062. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38084] EP250404a: Xinglong-2.16m spectroscopic redshift
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40061 SUBJECT: EP250404a: Xinglong-2.16m spectroscopic redshift DATE: 25/04/04 18:05:48 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> Z.P. Zhu, J. An, X. Liu, S.Q. Jiang, J.J. Jin, Z. Fan, D. Xu (NAOC), S.Y. Fu (HUST), report on behalf of a large collaboration: We carried out spectroscopy of the optical counterpart (e.g., Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058) of EP250404a (Hu et al., GCN 40051), likely the identical event to GRB 250404A (GBM team, GCN 40050), using the 2.16-m telescope equipped with the BFOSC instrument, located at Xinglong, Hebei, China. Our spectra cover the wavelength range 3800 - 9000 AA, and consist of 2 exposures of 1800 s each. The continuum is throughout the spectrum. From the detection of a broad Lya absorption feature at ~ 4400 AA and relatively weak absorption features, which interpreted as being due to Si IV and Al III, we infer a common redshift of z = 2.63. We conclude this is the likely redshift of the event. An intervening system is also detected with absorption features, interpreted as being due to Mg II and Fe II, we inferred its redshift of z = 1.88. We acknowledge the expert support from the Xinglong-2.16m staff, in particular Junjun Jia and Jie Zheng. View this GCN Circular online at https://gcn.nasa.gov/circulars/40061. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38083] GRB 250403A: Fermi GBM observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40060 SUBJECT: GRB 250403A: Fermi GBM observations DATE: 25/04/04 16:31:50 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH), M. Godwin (UAH), C. Meegan (UAH) and E. Bissaldi (Politecnico and INFN Bari) report on behalf of the Fermi GBM Team: "At 15:15:22.83 UT on 03 April 2025, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 250403A (trigger 765386127 / 250403636). This GRB was also detected by the SVOM (Julakanti et al. 2025, GCN 40026). The Fermi GBM Final Real-time Localization (GCN 40025) is consistent with the SVOM position. The angle from the Fermi LAT boresight at the GBM trigger time is 59 degrees. The GBM light curve consists of multiple pulses with a duration (T90) of about 16.4 s (50-300 keV). The time-averaged spectrum from T0-4.1 s to T0+14.3 s is best fit by a simple power law function with index -1.65 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (6.7 +/- 0.2)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.3 s in the 10-1000 keV band is 4.2 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40060. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38082] GRB 250327B: VIRT Optical Upper Limit
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40059 SUBJECT: GRB 250327B: VIRT Optical Upper Limit DATE: 25/04/04 16:21:28 GMT FROM: Priya Gokuldass at ERAU <gokuldap(a)my.erau.edu> K. Smith (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), B. Gendre (UVI), D. Morris (NASA), T. Lombardi (Eckerd College), F. George (ERAU), D. Smith (UVI), C. Watson (UVI) report: We observed the field of GRB 250327B (Bouchet et al., GCN 39888) detected by SVOM/ECLAIRs with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2025-03-28 starting at 06:52:58.6 (T-mid ~ T0 + 10.5 hrs). We performed a series of exposures in an R filter with a total exposure of 2560s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.6. We do not detect any source at the position reported by SAO/RAS (Moskvitin et al., GCN 39889). This non-detection is consistent with reported detections (Moskvitin et al., GCN 39889; Pankov et al., GCN 39906; Xin et al., GCN 39890; O’Neill et al., GCN 39891;Malesani et al., GCN 39893; Lian et al, GCN 39894; Shrestha et al., GCN 39896; Kumar et al., GCN 39904; Pérez-Fournon et al., GCN 39912; Ducoin et al., GCN 39897; Ducoin et. al., GCN 39930; Perley et al., GCN 39902; Dennefeld et al., GCN 39905; Tarasenkov et al., GCN 39913; Broens et. al., GCN 40006 and Siegel et. al., GCN 40009) and upper limits (Mo et. al., GCN 39914 and della Vecchia et. al., GCN 39969). We report the following 3-sigma upper limit: T_mid ||Exposure ||Filter ||Limit T+ 10.5 hrs || 2560 s || R || > 20.8 The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction. We acknowledge financial support from NASA EPSCoR award 80NNSC22M0063, NSF PAARE award 2319415, and NASA EPSCoR award 80NSSC24M0112. This message can be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40059. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38081] EP250404a: Mephisto multi-band optical detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40058 SUBJECT: EP250404a: Mephisto multi-band optical detection DATE: 25/04/04 16:19:08 GMT FROM: Chenxu Liu at Mephisto Team <cxliu(a)ynu.edu.cn> Guowang Du, Ziwei Li, Chenxu Liu, Dezi Liu, Yaosong Yu, Chenxi Shang, Jinghua Zhang, Yuan Fang, Xufeng Zhu, Tao Wang, Xinlei Chen, Xingzhu Zou, Yu Pan, Brajesh Kumar, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: We performed simultaneous multi-band photometric observations of EP250404a (EP-WXT ID: 01709133918) detected by EP (Hu et al., GCN 40051) and by Fermi/GBM (Fermi team, GCN 40050) with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at the Lijiang Observatory. The observations were initiated at 14:32:03UTC2025-04-04 (i.e., 723s after the EP/WXT trigger) and are still ongoing at the time of this report. Multiple frames were obtained in uvgriz- bands. The optical counterpart is clearly detected in all bands. The photometry of the initial frames is listed below: UT start |Band | Exp | Mag (AB) --------------------|-----|-------|----------|-------------------------- 2025/4/4 14:32:03 | u | 180s | 18.65+/-0.08 2025/4/4 14:32:04 | i | 79s | 14.60+/-0.01 2025/4/4 14:32:05 | g | 50s | 15.72+/-0.01 2025/4/4 14:39:20 | v | 180s | 16.91+/-0.02 2025/4/4 14:39:21 | z | 79s | 14.03+/-0.01 2025/4/4 14:39:22 | r | 50s | 14.83+/-0.01 Our results echo the detection from Nanshan/HMT (Jiang et al., GCN 40052) and BOOTES-4/MET (I. Perez-Garcia et al., GCN 40053). ---------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ---------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/40058. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38080] GRB 250331C Swift-BAT refined analysis
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40057 SUBJECT: GRB 250331C Swift-BAT refined analysis DATE: 25/04/04 16:17:44 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250331C (trigger #1299967) (Cenko, et al., GCN Circ. 39959). The BAT ground-calculated position is RA, Dec = 80.963, 33.068 deg which is RA(J2000) = 05h 23m 51.0s Dec(J2000) = +33d 04' 03.4" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a dim pulse of emission with some possible complex structure. The T90 (15-350 keV) is 70.10 +- 11.70 sec (estimated error including systematics). The time-averaged spectrum from T-12.59 to T+66.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.88 +- 0.23. The fluence in the 15-150 keV band is 6.6 +- 1.0 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-3.19 sec in the 15-150 keV band is 0.3 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1299967 View this GCN Circular online at https://gcn.nasa.gov/circulars/40057. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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