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[vsnet-grb-info 42088] GRB 260310B: GECAM-B observation of a burst
by GCN Circulars 12 Mar '26

12 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43967 SUBJECT: GRB 260310B: GECAM-B observation of a burst DATE: 26/03/12 05:08:05 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260310B, at 2026-03-10T21:41:26.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43955). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 46 +6/-7 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260310B.png 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/43967. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42087] Retraction of GCN 43965: GRB is actually solar flare
by GCN Circulars 12 Mar '26

12 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43966 SUBJECT: Retraction of GCN 43965: GRB is actually solar flare DATE: 26/03/12 03:36:34 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: The claimed GRB 260312A, reported in GCN Circular 43965, is found to be consistent with the location of the Sun and is due to a solar flare. View this GCN Circular online at https://gcn.nasa.gov/circulars/43966. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42086] GRB 260312A: Swift detection of a burst
by GCN Circulars 12 Mar '26

12 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43965 SUBJECT: GRB 260312A: Swift detection of a burst DATE: 26/03/12 03:17:24 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> N. J. Klingler (GSFC/UMBC/CRESSTII), C. Gronwall (PSU), R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 02:57:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260312A (trigger=1500106). Swift did not slew. The BAT on-board calculated location is RA, Dec 351.609, -3.533 which is RA(J2000) = 23h 26m 26s Dec(J2000) = -03d 31' 59" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. Swift automatic follow-up slews are currently disabled. Thus there will be no XRT or UVOT data for this trigger, which is also Sun constrained. Although Swift could not slew to confirm the GRB with an X-ray afterglow, the high significance in the BAT image (9.4 sigma) gives us confidence that this is an astrophysical source. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu) Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43965. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42085] GRB 260311B: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43964 SUBJECT: GRB 260311B: Fermi GBM Final Real-time Localization DATE: 26/03/11 19:08:31 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 18:57:55 UT on 11 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260311B (trigger 794948280.422386 / 260311790). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 278.5, Dec = 0.4 (J2000 degrees, equivalent to J2000 18h 33m, 0d 24'), with a statistical uncertainty of 11.7 degrees. The angle from the Fermi LAT boresight is 54.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311790/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311790/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260311790/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43964. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42084] GRB 260131A/B: radio detection with the VLA
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43963 SUBJECT: GRB 260131A/B: radio detection with the VLA DATE: 26/03/11 16:32:24 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 00:39:44 UT on 2026 February 5 (T_mid = 4.78 days post-burst) the Karl G. Jansky VLA observed the field of GRB 260131A/B (Fermi GBM team, GCN 43579, 43585; Sugai et al., GCN 43580; Konus-Wind team, GCN 43590; Insight-HXMT team, GCN 43591; GRID Collaboration, GCN 43605) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C48 was used as bandpass, flux density and phase calibrator. From a preliminary analysis, an unresolved radio source is detected at a position (J2000): RA: 01:38:51.308 +- 0.001 Dec: +34:19:40.84 +- 0.01 consistent with the X-ray (Sugai et al., GCN 43580; Jiang et al., GCN 43600;), optical (GOTO collaboration, GCN 43586; Lee et al., GCN 43587; García García, GCN 43599; Jayaraman et al., GCN 43606; Zhu et al., GCN 43607; KAIT GRB team, GCN 43609; MISTRAL GRB collaboration, GCN 43610; Volnova et al., GCN 43632, 43670; Gupta et al., GCN 43708) and infrared (Shi et al., GCN 43601) 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] ================================================================ 4.78 6 669 6 0.94x0.34 74 4.78 10 1018 6 0.60x0.21 70 4.78 15 1671 9 0.49x0.15 68 ================================================================ No source is detected with a >3sigma confidence level at the aforementioned position in the VLASS. 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/43963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42083] EP260302a: MeerKAT radio counterpart
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43962 SUBJECT: EP260302a: MeerKAT radio counterpart DATE: 26/03/11 15:56:12 GMT FROM: Francesco Carotenuto at INAF/OAR <francesco.carotenuto(a)inaf.it> F. Carotenuto (INAF-OAR), J. Bright (Oxford), P. G. Jonker (Radboud), on behalf of a larger collaboration We observed the field of EP260302a detected by the Einstein Probe (GCN 43899, 43906, 43932) with the MeerKAT radio telescope on 2026-03-10, from 18:00 UTC to 18:46 UTC (with a total time on source of 44 minutes) using the S-band receiver at a central frequency of 3.06 GHz. Analysing the SARAO Science Data Processor output continuum image we detect a source at the position of EP260302a (RA 08:51:53.7, DEC -65:59:01) with a flux density of around 170 uJy/beam, and with a typical image noise of around 8 uJy/beam. Further observations are planned. We thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the "MPIfR S-band receiver system" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society. View this GCN Circular online at https://gcn.nasa.gov/circulars/43962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42082] GRB260307A: GECAM-B observation of a burst
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43961 SUBJECT: GRB260307A: GECAM-B observation of a burst DATE: 26/03/11 14:52:31 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260307A, at 2026-03-07T11:27:59.350 UTC, which is also detected by Fermi/GBM (Fermi GBM team, GCN #43939). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses, with a duration (T90) of 4.5 +1.0/-0.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260307A.png 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/43961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42081] GRB 260308A: SVOM/GRM observation of a short GRB
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43960 SUBJECT: GRB 260308A: SVOM/GRM observation of a short GRB DATE: 26/03/11 14:33:12 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> SVOM/GRM team: Xing-Hao Luo, Chen-Wei Wang, Zheng-Hang Yu, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260308A (SVOM trigger reference: sb26030801) at 2026-03-08T20:05:53.100 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43949). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 1.50 +/-0.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260308A.png In addition, the position of this burst, as determined by Fermi/GBM (RA=250.2 , DEC=-32.6, Fermi GBM team, GCN #43949), is located at about 62 degrees form the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-0.8 to T0+0.4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.86 +0.18/-0.16 and the cutoff energy, parameterized as Epeak, is 643 +346/-180 keV. The localization of GRB 260308A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260308A_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 point of contact for this burst is: Xing-Hao Luo (luoxh(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43960. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42080] EP260306a: Mondy optical upper limit
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43959 SUBJECT: EP260306a: Mondy optical upper limit DATE: 26/03/11 10:31:25 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), E. Klunko (ISTP), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the fast X-ray transient EP260306a (Huang et al., GCNs 43930, 43937) using the AZT-33IK 1.5m telescope of the Mondy observatory on March 7, 8, and 9 taking several 120-seconds frames in the R band. In the stacked frame of the three epochs we do not detect the optical counterpart reported previously (Li et al., GCN 43929; Globus et al., GCN 43931; Ma et al., GCN 43933; Levan et al., GCN 43934). Preliminary photometry of the galaxy and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-03-07 15:44:24 1.61672 33*120 R n/d n/d 22.8 Mondy/AZT-33IK 2026-03-08 14:30:42 2.57040 40*120 R n/d n/d 22.1 Mondy/AZT-33IK 2026-03-09 16:24:33 3.64947 40*120 R n/d n/d 23.2 Mondy/AZT-33IK The photometry is based on nearby USNO-B1.0 stars (R2-magnitudes) and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42079] GRB 260310A: AstroSat CZTI detection of a long burst
by GCN Circulars 11 Mar '26

11 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43958 SUBJECT: GRB 260310A: AstroSat CZTI detection of a long burst DATE: 26/03/11 07:19:18 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S. Salunke (IUCAA), Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), A. Arya (IITB), A. Goyal (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 GRB 260310A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43951). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-03-10 04:57:12.05 UTC. The measured peak count rate associated with the burst is 273 (+67, -57) counts/s above the background in the combined data of all quadrants, with a total of 2709 (+573, -589) counts. The local mean background count rate was 1494 (+6, -6) counts/s. We measure a T90 of 30 (+2, -8) s from the cumulative Veto light curve. The source was also clearly detected in the 20-200 keV energy range. 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/43958. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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