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[vsnet-grb-info 42078] GRB 260311A: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43957 SUBJECT: GRB 260311A: Fermi GBM Final Real-time Localization DATE: 26/03/11 03:46:15 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 SHORT GRB At 03:35:40 UT on 11 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260311A (trigger 794892945.615954 / 260311150). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 291.3, Dec = -43.5 (J2000 degrees, equivalent to J2000 19h 25m, -43d 30'), with a statistical uncertainty of 10.8 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/2026/bn260311150/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311150/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311150/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43957. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42077] Fermi GRB 260310B: Global MASTER-Net observations report
by GCN Circulars 10 Mar '26

10 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43956 SUBJECT: Fermi GRB 260310B: Global MASTER-Net observations report DATE: 26/03/10 22:30:30 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260310B ( Fermi GBM team, GCN 43955) errorbox 542 sec after notice time and 552 sec after trigger time at 2026-03-10 21:50:36 UT, with upper limit up to 16.9 mag. The observations began at zenith distance = 59 deg. The sun altitude is -50.4 deg. The galactic latitude b = 21 deg., longitude l = 209 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3179876 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 582 | 2026-03-10 21:50:36 | MASTER-Kislovodsk | (07h 54m 35.80s , +13d 00m 23.6s) | C | 60 | 16.6 | 687 | 2026-03-10 21:52:21 | MASTER-Kislovodsk | (07h 58m 19.92s , +14d 56m 29.1s) | C | 60 | 16.9 | 790 | 2026-03-10 21:54:03 | MASTER-Kislovodsk | (07h 46m 02.42s , +14d 53m 53.7s) | C | 60 | 16.8 | 892 | 2026-03-10 21:55:45 | MASTER-Kislovodsk | (07h 51m 26.76s , +11d 07m 39.5s) | C | 60 | 16.5 | 1118 | 2026-03-10 21:59:32 | MASTER-Kislovodsk | (08h 03m 35.41s , +11d 08m 23.4s) | C | 60 | 16.6 | 1219 | 2026-03-10 22:01:12 | MASTER-Kislovodsk | (07h 50m 14.85s , +16d 47m 46.5s) | C | 60 | 16.5 | 1322 | 2026-03-10 22:02:55 | MASTER-Kislovodsk | (08h 02m 41.51s , +16d 48m 06.7s) | C | 60 | 16.7 | 1426 | 2026-03-10 22:04:39 | MASTER-Kislovodsk | (08h 10m 41.96s , +14d 55m 27.7s) | C | 60 | 16.8 | 1527 | 2026-03-10 22:06:20 | MASTER-Kislovodsk | (07h 39m 13.82s , +11d 06m 33.0s) | C | 60 | 16.6 | 1631 | 2026-03-10 22:08:04 | MASTER-Kislovodsk | (07h 48m 50.33s , +09d 12m 03.5s) | C | 60 | 16.5 | 1742 | 2026-03-10 22:09:56 | MASTER-Kislovodsk | (08h 00m 58.87s , +09d 12m 38.7s) | C | 60 | 16.7 | 1849 | 2026-03-10 22:11:42 | MASTER-Kislovodsk | (07h 37m 42.68s , +16d 48m 11.2s) | C | 60 | 16.7 | 1955 | 2026-03-10 22:13:28 | MASTER-Kislovodsk | (07h 33m 33.75s , +14d 52m 48.8s) | C | 60 | 16.5 | 2299 | 2026-03-10 22:19:12 | MASTER-Kislovodsk | (07h 30m 05.05s , +12d 59m 15.0s) | C | 60 | 16.2 | 2407 | 2026-03-10 22:21:00 | MASTER-Kislovodsk | (08h 15m 46.83s , +11d 07m 53.6s) | C | 60 | 16.6 | 2515 | 2026-03-10 22:22:48 | MASTER-Kislovodsk | (08h 15m 18.68s , +16d 48m 43.7s) | C | 60 | 16.4 | 2623 | 2026-03-10 22:24:36 | MASTER-Kislovodsk | (08h 19m 09.07s , +12d 59m 50.9s) | C | 60 | 16.8 | 2720 | 2026-03-10 22:26:13 | MASTER-Kislovodsk | (08h 07m 48.22s , +18d 41m 27.6s) | C | 60 | 16.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43956. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42076] GRB 260310B: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Mar '26

10 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43955 SUBJECT: GRB 260310B: Fermi GBM Final Real-time Localization DATE: 26/03/10 21:49:02 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 21:41:23 UT on 10 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260310B (trigger 794871688.893658 / 260310904). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 119.6, Dec = 12.9 (J2000 degrees, equivalent to J2000 07h 58m, 12d 54'), with a statistical uncertainty of 6.7 degrees. The angle from the Fermi LAT boresight is 68.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310904/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310904/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310904/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43955. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42075] Fermi GRB 260310A: Global MASTER-Net observations report
by GCN Circulars 10 Mar '26

10 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43954 SUBJECT: Fermi GRB 260310A: Global MASTER-Net observations report DATE: 26/03/10 16:32:56 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 260310A ( Fermi GBM team, GCN 43951) errorbox 39832 sec after notice time and 39865 sec after trigger time at 2026-03-10 16:01:36 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 36 deg. The sun altitude is -40.5 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260310A errorbox 40477 sec after notice time and 40510 sec after trigger time at 2026-03-10 16:12:21 UT, with upper limit up to 18.3 mag. Observations started at twilight. The observations began at zenith distance = 51 deg. The sun altitude is -12.2 deg. The galactic latitude b = 38 deg., longitude l = 118 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3178578 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 39895 | 2026-03-10 16:01:36 | MASTER-Tunka | (14h 43m 00.89s , +78d 55m 32.9s) | C | 60 | 19.9 | 39895 | 2026-03-10 16:01:36 | MASTER-Tunka | (14h 45m 33.78s , +78d 47m 59.9s) | C | 60 | 20.0 | 40197 | 2026-03-10 16:06:37 | MASTER-Tunka | (14h 33m 24.43s , +80d 47m 57.5s) | C | 60 | 19.1 | 40197 | 2026-03-10 16:06:37 | MASTER-Tunka | (14h 36m 13.25s , +80d 42m 38.1s) | C | 60 | 19.2 | 40540 | 2026-03-10 16:12:21 | MASTER-Kislovodsk | (13h 26m 03.01s , +78d 44m 12.4s) | C | 60 | 17.9 | 40643 | 2026-03-10 16:14:03 | MASTER-Kislovodsk | (14h 10m 06.46s , +76d 46m 16.8s) | C | 60 | 17.8 | 40749 | 2026-03-10 16:15:49 | MASTER-Kislovodsk | (14h 29m 09.94s , +78d 40m 44.7s) | C | 60 | 18.1 | 40850 | 2026-03-10 16:17:31 | MASTER-Kislovodsk | (13h 41m 13.66s , +80d 36m 24.9s) | C | 60 | 18.3 | 40941 | 2026-03-10 16:19:01 | MASTER-Kislovodsk | (13h 56m 38.66s , +74d 54m 16.8s) | C | 60 | 18.0 | 41046 | 2026-03-10 16:20:47 | MASTER-Kislovodsk | (14h 57m 06.59s , +80d 32m 41.8s) | C | 60 | 18.3 | 41150 | 2026-03-10 16:22:30 | MASTER-Kislovodsk | (15h 03m 52.45s , +76d 43m 39.0s) | C | 60 | 17.9 | 41357 | 2026-03-10 16:25:57 | MASTER-Kislovodsk | (14h 46m 01.37s , +74d 52m 17.5s) | C | 60 | 14.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43954. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42074] GRB 260307B: SVOM/ECLAIRs refined analysis
by GCN Circulars 10 Mar '26

10 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43953 SUBJECT: GRB 260307B: SVOM/ECLAIRs refined analysis DATE: 26/03/10 16:09:19 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, L. Bouchet (IRAP), F. Magnani, A. Foisseau (CPPM), report on behalf of the SVOM/ECLAIRs team. Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260307B (SVOM burst-id sb26030704 – GCN 43940, trigger time T0 = 2026-03-07T13:45:26 UTC), which was also detected by Fermi/GBM (GCN 43948). The burst that triggered ECLAIRs shows a single peak lightcurve lasting for around 41 s prior to the slew, followed by a featureless emission after the slew. The burst duration is estimated to be around 580 s in the 4-120 keV energy band through imaging. The time-averaged spectrum before the slew (from T0-24 s to T0+17 s) in the energy range 5-120 keV is best fitted by a powerlaw model with a photon index of -1.29 +/-0.10. With this model, the 4-120 keV fluence is (9.4 +0.5/-1.4)e-7 erg/cm^2 and the 4-120 keV photon flux is 0.54 +0.02/-0.06 ph/cm^2/s. The time-averaged spectrum after the slew (from T0+151 s to T0+560 s) in the energy range 5-120 keV is best fitted by a powerlaw model with an exponential cutoff. The photon index is -0.96 +0.37/-0.33 and the peak energy is 36 +38/-14 keV. With this model, the 4-120 keV fluence is (1.4 +0.1/-0.7)e-6 erg/cm^2 and the 4-120 keV photon flux is 0.12 +0.01/-0.06 ph/cm^2/s. Using the best fit parameter from the spectrum before the slew to fit the spectrum after the slew does not give a good fit (chi²/dof: 21.1/12), which implies the presence of a spectral evolution with time. 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: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/43953. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42073] GRB 260208A: radio detection with the VLA
by GCN Circulars 10 Mar '26

10 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43952 SUBJECT: GRB 260208A: radio detection with the VLA DATE: 26/03/10 09:40:09 GMT FROM: Stefano Giarratana at INAF-OAB <s.giarratana(a)ira.inaf.it> S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA), G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.), N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB), L. Nava (INAF-OAB) At 05:24:16 UT on 2026 February 10 (T_mid = 2.04 days post-burst) the Karl G. Jansky VLA observed the field of GRB 260208A (Fermi GBM team, GCN 43635, 43673; Fermi-LAT team, GCN 43645; GECAM team, GCN 43658; Waratkar et al., GCN 43674; Cheung et al., GCN 43675; Kirschner et al., GCN 43896) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C286 was used as bandpass, flux density and phase calibrator. From a preliminary analysis, an unresolved radio source is detected at a position (J2000): RA: 13:38:55.595 +- 0.001 Dec: +33:48:06.12 +- 0.01 consistent with the X-ray (Swift-XRT team, GCN 43652) and optical (Podesta et al., GCN 43640; GOTO collaboration, GCN 43641; SVOM/VT team, GCN 43655; ZTF collaboration, GCN 43657; Dimple et al., GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665; Volnova et al., GCN 43666, 43770, 43771; Bochenek et al., GCN 43676; Pérez-Fournon et al., GCN 43694; Swift/UVOT team, GCN 43702) position of the transient. The preliminary analysis yields the following results: ================================================================ T_mid Freq Peak r.m.s. Beam PA [days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg] ================================================================ 2.04 6 59 7 1.57x0.31 -60 2.04 10 90 8 1.27x0.18 -57 2.04 15 125 10 1.02x0.14 -55 ================================================================ No source is detected with a >3sigma confidence level at the aforementioned position in the VLASS. However, the r.m.s. noise level of the survey at the GRB location is approximately 130 uJy/b. We would like to thank the staff of the VLA for approving, executing, and processing the observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. These observations were carried out as part of project SF181027, approved in the framework of the Fermi - NRAO joint program agreement. View this GCN Circular online at https://gcn.nasa.gov/circulars/43952. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42072] GRB 260310A: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Mar '26

10 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43951 SUBJECT: GRB 260310A: Fermi GBM Final Real-time Localization DATE: 26/03/10 05:07:50 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 04:57:10 UT on 10 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260310A (trigger 794811435.80987 / 260310206). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 213.6, Dec = 78.7 (J2000 degrees, equivalent to J2000 14h 14m, 78d 42'), with a statistical uncertainty of 4.3 degrees. The angle from the Fermi LAT boresight is 124.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310206/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310206/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260310206/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43951. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42071] GRB 260307A: Glowbug gamma-ray detection
by GCN Circulars 09 Mar '26

09 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43950 SUBJECT: GRB 260307A: Glowbug gamma-ray detection DATE: 26/03/09 20:35:59 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, confirms the detection of GRB 260307A, which was detected by Fermi/GBM (GCN 43939) and CALET (Trigger 1456918069). The burst onset is at 2026-03-07 11:27:59.2 with a burst duration of 5.0s. 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/43950. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42070] GRB 260308A: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Mar '26

08 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43949 SUBJECT: GRB 260308A: Fermi GBM Final Real-time Localization DATE: 26/03/08 20:16:13 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 SHORT GRB At 20:05:52 UT on 8 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260308A (trigger 794693157.451346 / 260308837). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 250.2, Dec = -32.6 (J2000 degrees, equivalent to J2000 16h 40m, -32d 36'), with a statistical uncertainty of 3.6 degrees. The angle from the Fermi LAT boresight is 108.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260308837/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260308837/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260308837/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43949. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42069] Fermi GBM Sub-Threshold Detection of GRB 260307B
by GCN Circulars 08 Mar '26

08 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43948 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 260307B DATE: 26/03/08 15:14:09 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> R. Sonawane (IISER TVM), reports on behalf of the Fermi-GBM Team: SVOM/ECLAIRs detected the GRB 260307B on 2026-03-07 at 13:45:26 UTC (Magnani et al. 2026, GCN 43940). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified a candidate. The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient starting at 2026-03-07T13:45:30.6 (UTC), most significantly on the 32 s timescale, with a false alarm rate of 2.5e-04 Hz. The Fermi-MET of this transient is 794583935.8 s. The Targeted Search localization is found to be spatially consistent with the SVOM/ECLAIRs localization. Additionally, the GBM Targeted Search event was found with the highest significance using a "soft" spectrum (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43948. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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