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

[vsnet-grb-info 40244] GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
by GCN Circulars 09 Oct '25

09 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42174 SUBJECT: GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up DATE: 25/10/09 11:20:11 GMT FROM: Youdong HU at INAF-OAB <huyoudong072(a)hotmail.com> Y.-D. Hu (GXU), F. Aceituno, A. J. Castro-Tirado, E. Fernandez-Garcia, I. Perez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez, and S. Guziy (IAA-CSIC) and A. Fernández-Martín (CAHA) on behalf of a larger collaboration, report: Following the detection of GRB 251007A by Swift (Ambrosi et al. GCNC 42146), we triggered the 1.5m OSN telescope in Granada (Spain) starting on Oct. 08 at 04:17:06 UT (~8.8 hrs post burst), a series of I-band image was gathered. In the stacked image, the optical afterglow is detected within the Swift/XRT error region (Beardmore et al. GCNC 42161) with I=21.21+-0.19. About 20 mins later, the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain) also triggered to start taking images with Sloan-griz filters. The optical afterglow is detected in the stacked image with i=22.0+-0.3. These detections are consistent with the reports from UVOT (Ambrosi et al. GCNC 42146), MASTER (Lipunov et al. GCNC 42149), SVOM/C-GFT (Wu et al. GCNC 42154), AKO (Odeh et al. GCNC 42157), NOT (Malesani et al. GCNC 42158) and SVOM/VT (Li et al. GCNC 42163). We thank the staff at OSN and Calar Alto observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42174. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40243] GRB 251002A - SVOM/ECLAIRs refined analysis
by GCN Circulars 09 Oct '25

09 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42173 SUBJECT: GRB 251002A - SVOM/ECLAIRs refined analysis DATE: 25/10/09 06:55:38 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. G. Bernardini (INAF-OAB, LUPM), U. Jacob, F. Piron (LUPM), M. Brunet, O. Godet (IRAP), N. Dagoneau, B. Hubert, S. Schanne, A. Saccardi, D. Gotz (CEA/Irfu) Using the event-by-event data downloaded through the X-band ground stations, we report further analysis of ECLAIRs observations of GRB 251002A (SVOM burst-id sb25100211). The burst that triggered ECLAIRs onboard (Saccardi et al., GCN Circ. 42060) consists of a multiple peak structure with a duration of T90 = (8.2 -0.3/+1.82) s in the 4-120 keV energy band. After this main emission episode, the source is still visible through image deconvolution as a dim source up to about 30 s after T0 (T0 = 2025-10-02T20:14:54 s). The time-averaged spectrum from T0-3 s to T0+8 s in the energy range 5-120 keV is best fitted by a cutoff power law model with index (0.72 +0.18/-0.20) and E0 = (79 +68/-26) keV. With this model, the total 4-120 keV fluence is (2.57 +/-0.03)e-6 erg/cm^2. All the quoted errors are at the 68% confidence level. 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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: M. G. Bernardini (INAF-OAB, LUPM) (maria.bernardini at inaf.it) View this GCN Circular online at https://gcn.nasa.gov/circulars/42173. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40242] IceCube alert 141456_888784 retraction
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42172 SUBJECT: IceCube alert 141456_888784 retraction DATE: 25/10/08 23:19:08 GMT FROM: Erik Blaufuss at University of Maryland, College Park <blaufuss(a)umd.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 8 Oct 2025 at 22:35:50 UT IceCube issued an alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141456_888784.amon) reporting the detection of a neutrino candidate event with a moderate chance of being of astrophysical origin. Upon further examination by the IceCube collaboration, the event data was incomplete and clear classification of this event is not possible. At the time of this alert, the detector was operating with several portions of the detector removed from data taking due to hardware issues. Normally, these periods of operation are excluded from generating alerts. We apologize for any confusion this error may have caused. 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/42172. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40241] IceCube Alert 251008.94: Global MASTER-Net observations report
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42171 SUBJECT: IceCube Alert 251008.94: Global MASTER-Net observations report DATE: 25/10/08 23:00:30 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the IceCube Alert 251008.94 (trigger No 888784,02h 10m 30.00s , -37d 22m 58.8s, R=0.82) errorbox 12 sec after notice time and 77 sec after trigger time at 2025-10-08 22:37:08 UT, with upper limit up to 14.9 mag. The observations began at zenith distance = 80 deg. The sun altitude is -47.1 deg. The galactic latitude b = -70 deg., longitude l = 248 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3010374 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 87 | 2025-10-08 22:37:08 | MASTER-Kislovodsk | (02h 10m 07.45s , -37d 12m 08.1s) | P- | 20 | 13.5 | 87 | 2025-10-08 22:37:08 | MASTER-Kislovodsk | (02h 10m 20.29s , -36d 49m 52.3s) | P| | 20 | 14.0 | 127 | 2025-10-08 22:37:48 | MASTER-Kislovodsk | (02h 10m 07.61s , -37d 12m 10.0s) | P- | 20 | 13.6 | 127 | 2025-10-08 22:37:48 | MASTER-Kislovodsk | (02h 10m 20.57s , -36d 49m 54.1s) | P| | 20 | 14.1 | 172 | 2025-10-08 22:38:27 | MASTER-Kislovodsk | (02h 10m 07.83s , -37d 12m 11.4s) | P- | 30 | 13.5 | 172 | 2025-10-08 22:38:27 | MASTER-Kislovodsk | (02h 10m 20.85s , -36d 49m 55.6s) | P| | 30 | 14.4 | 227 | 2025-10-08 22:39:17 | MASTER-Kislovodsk | (02h 10m 08.11s , -37d 12m 12.6s) | P- | 40 | 14.1 | 227 | 2025-10-08 22:39:17 | MASTER-Kislovodsk | (02h 10m 21.18s , -36d 49m 56.7s) | P| | 40 | 14.5 | 291 | 2025-10-08 22:40:17 | MASTER-Kislovodsk | (02h 10m 08.36s , -37d 12m 14.0s) | P- | 50 | 13.9 | 292 | 2025-10-08 22:40:17 | MASTER-Kislovodsk | (02h 10m 21.52s , -36d 49m 58.2s) | P| | 50 | 14.4 | 366 | 2025-10-08 22:41:27 | MASTER-Kislovodsk | (02h 10m 08.70s , -37d 12m 15.9s) | P- | 60 | 14.1 | 366 | 2025-10-08 22:41:27 | MASTER-Kislovodsk | (02h 10m 21.96s , -36d 49m 59.9s) | P| | 60 | 14.6 | 456 | 2025-10-08 22:42:47 | MASTER-Kislovodsk | (02h 10m 09.11s , -37d 12m 17.3s) | P- | 80 | 14.1 | 456 | 2025-10-08 22:42:47 | MASTER-Kislovodsk | (02h 10m 22.44s , -36d 50m 01.3s) | P| | 80 | 14.8 | 566 | 2025-10-08 22:44:27 | MASTER-Kislovodsk | (02h 10m 09.54s , -37d 12m 20.0s) | P- | 100 | 14.0 | 566 | 2025-10-08 22:44:27 | MASTER-Kislovodsk | (02h 10m 22.97s , -36d 50m 03.9s) | P| | 100 | 14.6 | 696 | 2025-10-08 22:46:26 | MASTER-Kislovodsk | (02h 10m 10.14s , -37d 12m 22.6s) | P- | 120 | 14.1 | 696 | 2025-10-08 22:46:27 | MASTER-Kislovodsk | (02h 10m 23.63s , -36d 50m 06.1s) | P| | 120 | 14.7 | 836 | 2025-10-08 22:48:46 | MASTER-Kislovodsk | (02h 10m 10.74s , -37d 12m 24.9s) | P- | 120 | 14.1 | 836 | 2025-10-08 22:48:46 | MASTER-Kislovodsk | (02h 10m 24.29s , -36d 50m 07.9s) | P| | 120 | 14.7 | 975 | 2025-10-08 22:51:06 | MASTER-Kislovodsk | (02h 10m 11.30s , -37d 12m 26.4s) | P- | 120 | 14.1 | 976 | 2025-10-08 22:51:06 | MASTER-Kislovodsk | (02h 10m 24.93s , -36d 50m 08.8s) | P| | 120 | 14.8 | 1115 | 2025-10-08 22:53:25 | MASTER-Kislovodsk | (02h 10m 11.90s , -37d 12m 27.9s) | P- | 120 | 14.1 | 1115 | 2025-10-08 22:53:26 | MASTER-Kislovodsk | (02h 10m 25.56s , -36d 50m 10.6s) | P| | 120 | 14.9 | The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42171. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40240] GRB 251003A: Fermi GBM Observation
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42170 SUBJECT: GRB 251003A: Fermi GBM Observation DATE: 25/10/08 18:10:09 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:58:31.96 UT on 03 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251003A (trigger 781149516/251003082), which was also detected by Swift BAT (A. P. Beardmore et al. 2025, GCN 42070). The Fermi GBM on-ground location is consistent with the Swift BAT position. GTC/OSIRIS+ detected a spectroscopic redshift z = 4.412 (R. Sanchez-Ramirez et al. 2025, GCN 42086). The angle from the Fermi LAT boresight is 56 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 10 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+6.1 s is best fit by a simple power law function with index -1.7 +/- 0.1. A Comptonized function fits equally well with a Epeak of 118 +/- 35 and alpha of -1.3 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (1.1 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.5 s in the 10-1000 keV band is 1.6 +/- 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/42170. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40239] GRB 251003A: Fermi GBM Observation
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42170 SUBJECT: GRB 251003A: Fermi GBM Observation DATE: 25/10/08 18:10:09 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:58:31.96 UT on 03 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251003A (trigger 781149516/251003082), which was also detected by Swift BAT (A. P. Beardmore et al. 2025, GCN 42070). The Fermi GBM on-ground location is consistent with the Swift BAT position. GTC/OSIRIS+ detected a spectroscopic redshift z = 4.412 (R. Sanchez-Ramirez et al. 2025, GCN 42086). The angle from the Fermi LAT boresight is 56 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 10 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+6.1 s is best fit by a simple power law function with index -1.7 +/- 0.1. A Comptonized function fits equally well with a Epeak of 118 +/- 35 and alpha of -1.3 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (1.1 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.5 s in the 10-1000 keV band is 1.6 +/- 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/42170. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40238] GRB 251006B: Fermi GBM Observation
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42169 SUBJECT: GRB 251006B: Fermi GBM Observation DATE: 25/10/08 18:01:32 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 20:05:04.04 UT on 06 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251006B (trigger 781473909/251006837), which was also detected by Einstein Probe (Yin et al. 2025, GCN 42137) and SVOM/GRM (Wang et al. 2025, GCN 42139). The Fermi GBM on-ground location is consistent with the EP position. The angle from the Fermi LAT boresight is 104 degrees. The GBM light curve consists of one bright emission with a weaker secondary peak with total duration (T90) of about 5.9 s (50-300 keV). The time-averaged spectrum from T0-2.0 to T0+7.2 s is best fit by a Band function with Epeak = 330 +/- 14 keV, alpha = -0.61 +/- 0.03, and beta = -2.4 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (2.06 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.38 s in the 10-1000 keV band is 26.2 +/- 0.4 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/42169. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40237] GRB 251007B: COLIBRÍ optical upper limit
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42168 SUBJECT: GRB 251007B: COLIBRÍ optical upper limit DATE: 25/10/08 15:32:24 GMT FROM: Francesco at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work(a)gmail.com> Francesco Magnani (CPPM), Camila Angulo (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), , Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the Swift/SVOM GRB 251007B (Melandri et al., GCN Circ. 42147, Webb et al., GCN Circ. 42148) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-08 10:34 to 12:32 UTC (from 14.9 to 16.8 hours after the trigger) and obtained 80 minutes of simultaneous exposure in the i and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and the tenue software, and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect a source at the SVOM/VT source position (Li et al., GCN Circ. 42163) down to the following 3-sigma limits: i > 23.3 z > 22.7 These upper limits are consistent with the ones reported by Wu et al. (GCN Circ. 42150). Our image is not deep enough to confirm fading of the source reported by Li et al. (GCN Circ. 42163). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/42168. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40236] GRB 251007A: AstroSat CZTI detection
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42167 SUBJECT: GRB 251007A: AstroSat CZTI detection DATE: 25/10/08 12:42:43 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), U. Pathak (IITB), G. Waratkar (Caltech/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 251007A which was also detected by Swift/BAT (GCN Circ. 42146), Glowbug (GCN Circ. 42151) and Calet GBM (GCN Circ. 42156). 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 2025-10-07 19:37:51.50 UTC. The measured peak count rate associated with the burst is 579 (+44, -41) counts/s above the background in the combined data three quadrants out of four, with a total of 4746 (+253, -236) counts. The local mean background count rate was 186 (+1, -2) counts/s. Using cumulative rates, we measure a T90 of 17.5 (+4.1, -1.3) 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 2025-10-07 19:37:49.6 UTC. The measured peak count rate associated with the burst is 1557 (+83, -88) counts/s above the background in the combined data of all quadrants, with a total of 9759 (+524, -526) counts. The local mean background count rate was 1146 (+3, -4) counts/s. We measure a T90 of 16.9 (+6.6, -1.3) 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/42167. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40235] GRB 251006B/EP251006a: EP-FXT afterglow detection
by GCN Circulars 08 Oct '25

08 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42166 SUBJECT: GRB 251006B/EP251006a: EP-FXT afterglow detection DATE: 25/10/08 11:48:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), M. H. Zhang, T. Y. Liu, H. Y. Ren and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a second follow-up observation of GRB 251006B/EP251006a (GCN 42131, GCN 42137, GCN 42139, GCN 42155) at 2025-10-07T18:08:41 (UTC), about 22 hours after the WXT detection, with an exposure time of 4.9 ks. The source was also followed by several optical telescopes (GCN 42133, GCN 42138, GCN 42141). Two uncatalogued sources were detected within the WXT error circle (GCN 42140), of which Source 2 has faded with an unabsorbed flux of 3.37 x 10^-13 erg/s/cm^2 (22 hours) from the first observation at about 3.52 x 10^-12 erg/s/cm^2 (11 hours) in 0.5-10 keV. The position of Source 2 is R.A. = 40.5195 deg, DEC = -6.0346 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic), which is consistent with the SVOM/VT optical candidate (GCN 42141), and is therefore likely the GRB afterglow. 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/42166. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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