April 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[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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