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

[vsnet-grb-info 40264] Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42194 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB DATE: 25/10/10 23:06:32 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 781824269/251010892 at 21:24:24.75 UT on 10 October 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/42194. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40263] GRB 251007B: Swift/UVOT Upper Limits
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42193 SUBJECT: GRB 251007B: Swift/UVOT Upper Limits DATE: 25/10/10 18:00:23 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> GRB 251007B: Swift/UVOT Upper Limits M. H. Siegel (PSU) and A. Melandri (INAF-OAR) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251007B 152 s after the BAT trigger (Melandri et al., GCN Circ. 42147). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ 42159) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 152 302 147 >19.8 u_FC 311 561 246 >19.1 white 152 5220 220 >19.9 v 641 4360 220 >19.2 b 567 5181 236 >20.3 u 311 4975 462 >19.5 w1 691 4770 216 >19.8 m2 665 4565 216 >19.5 w2 616 810 39 >18.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.786 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42193. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40262] GRB 251010A: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42192 SUBJECT: GRB 251010A: Fermi GBM Final Real-time Localization DATE: 25/10/10 17:55:05 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 17:44:25 UT on 10 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251010A (trigger 781811070.725816 / 251010739). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 214.0, Dec = 56.6 (J2000 degrees, equivalent to J2000 14h 16m, 56d 36'), with a statistical uncertainty of 4.5 degrees. The angle from the Fermi LAT boresight is 103.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251010739/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251010739/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251010739/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42192. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40261] GRB251007A: Swift/UVOT Detection
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42191 SUBJECT: GRB251007A: Swift/UVOT Detection DATE: 25/10/10 17:40:49 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) and E/ Ambrosi (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251007A 79 s after the BAT trigger (Ambrosi et al., GCN Circ. 42146). A fading source consistent with the XRT position (Beardmore et al., GCN Circ. 42161) and the previously reported optical source (Wu et al., GCN Circ. 42154; Malesani et al., GCN Circ. 42158, Hu et al. GCN Circ 42174) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 08:32:42.39 = 128.17664 (deg.) Dec (J2000) = +21:48:46.3 = 21.81285 (deg.) with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence). Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 80 229 146 18.42+/-0.08 white 17739 18156 406 >20.41 v 11939 39105 2335 >20.09 b 16827 17734 885 >20.39 u 291 418 124 19.11+/-0.36 uvm2 27913 39155 906 >20.29 uvw2 23059 34819 1506 >20.58 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42191. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40260] GRB 251009A: GECAM-B detection of a short burst
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42190 SUBJECT: GRB 251009A: GECAM-B detection of a short burst DATE: 25/10/10 16:22:21 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by the short burst GRB 251009A at 2025-10-09T15:58:56.300 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179), SVOM/GRM (Wang et al., GCN#42185) and Insight-HXMT (Wang et al., GCN#42189). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 0.14 +0.08/-0.08 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251009A.png Using the automatic on-ground localization pipeline, GECAM-B localized this burst to the following position (J2000): Ra: 103.2 deg Dec: 34.2 deg Err: 21.4 deg (1-sigma, statistical only) Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/42190. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40259] GRB 251009A: Insight-HXMT detection of a short burst
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42189 SUBJECT: GRB 251009A: Insight-HXMT detection of a short burst DATE: 25/10/10 16:17:00 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-10-09T15:58:56.350 (T0), Insight-HXMT/HE detected the burst GRB 251009A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179) and SVOM/GRM (Wang et al., GCN#42185). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.65 +0.31/-0.28 s. The total counts from this burst is 998 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251009A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/42189. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40258] GRB 251009B (short): Glowbug gamma-ray detection
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42188 SUBJECT: GRB 251009B (short): Glowbug gamma-ray detection DATE: 25/10/10 16:14:04 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251009B, which was also detected by Insight-HXMT (GCN 41287). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-09 01:51:14.176 with a duration of 1.0 s and a total significance of about 13.1 sigma. The light curve comprises two peaks at ~T0+0.2s and ~T0+0.9s. The best-fit localization is RA, Decl. (J2000, deg) = 155.1, 24.1 with a radius of 25.3 deg (95% confidence), with a highly uncertain systematic uncertainty. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS, and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42188. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40257] GRB 251009B: Insight-HXMT detection of a short burst
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42187 SUBJECT: GRB 251009B: Insight-HXMT detection of a short burst DATE: 25/10/10 15:50:38 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-10-09T01:51:15.250 (T0), Insight-HXMT/HE detected the burst GRB 251009B, which is also detected by SVOM/GRM. The Insight-HXMT/HE light curve mainly consists of double pulses with a T90 of 1.00 +0.15/-0.05 s. The total counts from this burst is 2442 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251009B.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/42187. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40256] GRB 251007A: Swift-BAT refined analysis
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42186 SUBJECT: GRB 251007A: Swift-BAT refined analysis DATE: 25/10/10 14:08:25 GMT FROM: Takanori Sakamoto at AGU <tsakamoto(a)phys.aoyama.ac.jp> S. Laha (GSFC/UMBC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), 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-240 to T+303 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251007A (trigger #1402466) (Ambrosi, et al., GCN Circ. 42146). The BAT ground-calculated position is RA, Dec = 128.162, 21.810 deg which is RA(J2000) = 08h 32m 38.8s Dec(J2000) = +21d 48' 36.6" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 85%. The mask-weighted light curve shows a complex structure starting at ~T-1 sec, peaking at T+56 sec, and decaying to background at T+110 sec. T90 (15-350 keV) is 64.19 +- 5.17 sec (estimated error including systematics). The time-averaged spectrum from T-0.04 to T+103.43 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.32 +- 0.03. The fluence in the 15-150 keV band is 1.04 +- 0.02 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from T+56.14 sec in the 15-150 keV band is 9.5 +- 0.3 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/1402466 View this GCN Circular online at https://gcn.nasa.gov/circulars/42186. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40255] GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42185 SUBJECT: GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission DATE: 25/10/10 13:32:03 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shu-Xu Yi, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short burst GRB 251009A (SVOM trigger reference: sb25100902) at 2025-10-09T15:58:56.500 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike followed by a weak tail emission with a T90 of 0.32 +0.05/-0.11 s in the 15-5000 keV band, which is somewhat similar to extragalactic magnetar giant flare. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251009A.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 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/42185. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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