March 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 42170] GRB 260318A: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44049 SUBJECT: GRB 260318A: Fermi GBM Final Real-time Localization DATE: 26/03/18 22:46:23 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 22:35:47 UT on 18 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260318A (trigger 795566152.456906 / 260318942). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 303.6, Dec = 57.0 (J2000 degrees, equivalent to J2000 20h 14m, 57d 00'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 17.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260318942/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260318942/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260318942/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44049. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42169] IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44048 SUBJECT: IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility DATE: 26/03/18 18:09:53 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Akshay Eranhalodi (DESY), Robert Stein (JSI), Jannis Necker (Leiden University), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260315A (Zegarelli et. al, GCN 44017) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-03-15 07:45 UTC, approximately 5.4 hours after event time. We covered 93.7% (0.7 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. We do not recover the previously reported candidate counterpart AT 2026fpm (Lipunov et al. 2026, GCN 44023) because it lies outside of the 90% contianment area based on the publicly available probability map of the neutrino event localisation. As the source is also likely a known variable (Fortin et al. 2026, GCN 44026; Feng et al., GCN 44042) it is unlikely to be the neutrino counterpart. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/44048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42168] Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44047 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB DATE: 26/03/18 15:31:39 GMT FROM: oliver.roberts(a)universityofgalway.ie O.J. Roberts (Uni. of Galway, Ireland) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger GRB 260313A (trigger 795096033/260312500) at 12:00:28.58 UT on 13 March 2026, tentatively classified as a GRB (GCN 43995, GCN 43987), is in fact unlikely to be a GRB. The nature of this trigger is uncertain." View this GCN Circular online at https://gcn.nasa.gov/circulars/44047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42167] GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44046 SUBJECT: GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate DATE: 26/03/18 12:06:23 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Francis Fortin (IRAP), Diego López-Cámara (UNAM), Jean-Grégoire Ducoin (CPPM), Antonio de Ugarte Postigo (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Missimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM) and Benjamin Schneider (LAM) report: We imaged the field of the GRB 260316A / EP260316a (Jiang et al., GCN Circ. 44027, GCN Circ. 44034) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-03-18 07:20:28 to 09:50:38 UTC (from 42.8 to 45.3 hours after the trigger) and obtained 111 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025) and the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We still detect the optical counterpart candidate that we previously reported in Fortin et al., GCN Circ. 44037. Template subtraction from 2026-03-17 to 2026-03-18 shows no significant residuals between the two epochs, and therefore does not allow us to conclude on the potential variability of this source. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. 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/44046. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42166] GRB 260310A / AT 2026fgk: radio detection with the VLA
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44045 SUBJECT: GRB 260310A / AT 2026fgk: radio detection with the VLA DATE: 26/03/18 09:14:01 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 10:22:44 UT on 2026 March 14 (T_mid = 4.26 days post-burst) the Karl G. Jansky VLA observed the field of GRB 260310A / AT 2026fgk (Fermi GBM team, GCN 43951, 43975; AstroSat CZTI collaboration, GCN 43958) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C286 was used as bandpass and flux density calibrator, while J1435+7605 served as phase calibrator. From a preliminary analysis, an unresolved radio source (Rhodes et al., GCN 44005) is clearly detected at all frequencies at a position: RA: 14:37:16.1424 +- 0.001 Dec: +71:50:30.328 +- 0.01 consistent with the X-ray (Jayaraman et al., GCN 43994) and optical (Hinds et al., AstroNote 2026-65, GCN 43977; Konno et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979, 44000; Moreno Méndez et al, GCN 43980; Becerra et al., GCN 43991; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo et al., GCN 44003; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022) and infrared (Li et al., GCN 43993; Stein et al., GCN 43996; Brivio et al., GCN 44004) 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] ================================================================ 4.26 6 3894 8 0.39x0.29 -31 4.26 10 6368 13 0.24x0.19 3.9 4.26 15 9104 29 0.16x0.11 -11 ================================================================ 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/44045. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42165] GRB 260310A / AT2026fgk: SVOM/VT optical observations
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44044 SUBJECT: GRB 260310A / AT2026fgk: SVOM/VT optical observations DATE: 26/03/18 07:47:29 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu)，J. X. Cao (GXU) report on behalf of the SVOM/VT team. SVOM/VT performed several ToO observations of the field of GRB 260310A detected by Fermi (Fermi GBM team, GCN 43951) and AstroSat(Salunke et al., GCN 43958) from 2026-03-14 to 2026-03-17 in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The reported optical counterpart AT2026fgk discovered by GOTO(O'Neill et al. 2026, TNS Discovery Report 294132) and observed by other observatories (Lipunov et al., GCN 43954; Konno et al., GCN 43974, Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979, Moren Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984, Pursiainen et al., Becerra et al., GCN 43991; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; L. Izzo, GCN 44003; Brivio et al., GCN 44004; Rhodes et al., GCN 44005; Moskvitin et al., GCN 44006; Brosio et al., GCN 44021; Pawar et al., GCN 44022; Belkin and Shrestha, GCN 44043) is clearly detected in single frames in both channels. The preliminary measurements in AB magnitudes are given below: Mid_time Band Exposure Time Magnitude (AB) 5.26 day VT_R 70 sec 18.44 +/- 0.05 mag 5.26 day VT_B 70 sec 18.94 +/- 0.05 mag 7.35 day VT_R 70 sec 18.65 +/- 0.05 mag 7.35 day VT_B 70 sec 19.15 +/- 0.05 mag Our photometry was not corrected for Galactic extinction. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/44044. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42164] GRB 260310A / AT2026fgk: LCO optical observations
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44043 SUBJECT: GRB 260310A / AT2026fgk: LCO optical observations DATE: 26/03/18 06:59:09 GMT FROM: Sergey Belkin at Monash University <sergey.belkin(a)monash.edu> S. Belkin and M. Shrestha (Monash U) report: We observed the optical counterpart AT2026fgk of GRB 260310A, detected by Fermi/GBM (Fermi GBM Team, GCN 43951) and AstroSat/CZTI (Salunke et al., GCN 43958), with the Las Cumbres Observatory 1m telescope at McDonald Observatory equipped with the Sinistro instrument. Observations began on 2026-03-14 at 06:12:09 UT, approximately 4.05 days after the trigger. We obtained 4 x 60 s exposures in the r band and 6 x 60 s exposures in the u band. In the stacked images we clearly detect the reported optical counterpart AT2026fgk (e.g. Lipunov et al., GCN 43954; Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Moreno Mendez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo, GCN 44003; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022), discovered by GOTO (O’Neill et al., TNS Discovery Report 294132). The preliminary photometry from the stacked images is: Date (UT) T-T0 (days) Filter Exp. time (s) Magnitude 3-sigma UL ======================================================================================== 2026-03-14 06:14:13 4.0535 r 60 x 4 18.58 +/- 0.02 21.79 2026-03-14 06:21:49 4.0588 u 60 x 6 19.47 +/- 0.04 21.12 The r-band photometry is calibrated against Pan-STARRS field stars. The u-band photometry is calibrated against Gaia DR3 synthetic SDSS u-band stars. The quoted values are not corrected for Galactic extinction. Further follow-up is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44043. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42163] IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44042 SUBJECT: IceCube-260315A/AT2026fpm: EP-FXT follow-up observation DATE: 26/03/18 04:57:04 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. P. Feng, B. Zhang (USTC), H. N. Yang, Y. Liu (NAO, CAS) The Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) performed a follow-up observation of AT2026fpm (Segura et al., GCN 44023) at UTC 2026-03-16T23:31:53 (T0+45.21h) (The IceCube Collaboration, GCN 44017). An X-ray source was detected at R.A. = 176.1586 deg, DEC = -2.6035 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic) and the flux of 1.1×10^(-13) erg/s/cm^2 in 0.5-10 keV band. The X-ray position is consistent with the optical transient AT2026fpm, which is spatially consistent with a QSO at z=1.389. 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/44042. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42162] GRB 260317A: Fermi GBM Final Localization
by GCN Circulars 17 Mar '26

17 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44041 SUBJECT: GRB 260317A: Fermi GBM Final Localization DATE: 26/03/17 21:55:00 GMT FROM: rhamburg(a)usra.edu The Fermi GBM team reports the detection of a likely SHORT GRB. "At 20:01:51.98 UT on 17 March 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260317A (trigger 795470516/260317835). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 255.62, Dec = -18.51 (J2000 degrees, equivalent to J2000 17h 2m, -18d 30'), with a statistical uncertainty of 13.33 degrees. The angle from the Fermi LAT boresight is 93 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260317835/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260317835/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260317835/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44041. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42161] GRB 260316A: GECAM-B observation
by GCN Circulars 17 Mar '26

17 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44040 SUBJECT: GRB 260316A: GECAM-B observation DATE: 26/03/17 15:46:38 GMT FROM: Yue Wang <m18509381757(a)163.com> Yue Wang, Chao Zheng, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260316A at 2026-03-16T17:12:53.100 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44031) and SVOM/GRM (Yue Wang et. al., GCN #44039). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 2.4 +0.4/-0.4 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260316A.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/44040. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0