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[vsnet-grb-info 42175] The EP-WXT trigger 01709258989 is likely a flaring star
by GCN Circulars 20 Mar '26

20 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44054 SUBJECT: The EP-WXT trigger 01709258989 is likely a flaring star DATE: 26/03/20 03:33:53 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou, Y. Wang, Q. J. Huang (PMO, CAS), J. P. Chen (SYSU), H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709258989 at the time of 2026-03-20T02:33:39 UTC, EP-FXT performed an automatic follow-up observation, and detected a source at RA: 112.7520 deg, Dec: 46.0075 deg, is likely a stellar flare associated with 1RXS J073101.9+460030. The estimated flux of the flare is around 1.0 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 3.6 x 10^31 erg/s. 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/44054. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42174] GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
by GCN Circulars 20 Mar '26

20 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44053 SUBJECT: GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90 DATE: 26/03/20 01:38:39 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> P. Minaev (IKI) , A. Pozanenko (IKI) on behalf of GRB follow-up team We analyzed GRB 260310A (Hamburg et al., GCN 43975; Salunke et al., GCN 43958; Atteia et al., GCN 43981) using publicly available data of GBM/Fermi. The burst consists of several emission episodes with a total duration of T_90 = 86 s. Time integrated energy spectrum, constructed in the time interval (-4, 70) s since GBM trigger, is best described by Band model with E_p = 175 keV and fluence F = 1.74e-5 erg cm^-2 in 1 keV - 10 MeV range. Using z = 0.153 (Hinds et al., GCN 43977; de Ugarte Postigo et al., GCN 43984) we obtain E_iso = 9.8e50 erg. GRB 260310A is placed above the correlation fit for type II (long) bursts on Ep,i – Eiso diagram, as mentioned in (Atteia et al., GCN 43981), but it is inside 2 sigma correlation regions for both type I (short) and type II (long) bursts, therefore we cannot consider it as a clear outlier. Indeed, at the EH – T_90,i diagram (see [1-2] for details) GRB 260310A is well classified as type II (long) burst. The Ep,i – Eiso and EH - T90,i diagrams can be found at https://heaiki.ru/lvc/GRB260310A/ [1] - Minaev et al., MNRAS, 492, 1919, 2020 [2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020 View this GCN Circular online at https://gcn.nasa.gov/circulars/44053. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42173] GRB 260318A: GECAM-B observation
by GCN Circulars 19 Mar '26

19 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44052 SUBJECT: GRB 260318A: GECAM-B observation DATE: 26/03/19 15:47:49 GMT FROM: yzh807926(a)163.com Zheng-Hang Yu, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260318A, at 2026-03-18T22:35:52.600 UTC (denoted as T0), which is also detected by Fermi/GBM ((Fermi GBM team, GCN #44049). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 19.5 +3.0/-2.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260318A.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/44052. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42172] GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
by GCN Circulars 19 Mar '26

19 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44051 SUBJECT: GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT DATE: 26/03/19 14:57:05 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Kumar Pranshu, Dhruv Jain, Debalina Kar, Pankaj Pawar, and Kuntal Misra (ARIES) report: We observed the field of GRB260310A/AT2026fgk detected by Fermi/GBM (Fermi GBM team, GCN 43951) and AstroSat(Salunke et al., GCN 43958) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2026-03-17 at 20:33:36.00 UT, i.e., ~ 7.65 days after the Fermi/GBM trigger. We have taken multiple frames with an exposure time of 300s in the I filter. We stacked the images after the alignment. We detect an optical afterglow in our stacked image. We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================ 2026-03-17 20:33:36.00 ~7.65 I 300s*3 18.01 +/-0.02 The optical detection of the burst is consistent with 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, 44000; Moreno Méndez et al., GCN 43980; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein et al., GCN 43996; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo et al., GCN 44003; Brivio et al., GCN 44004; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044. The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/44051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42171] Fermi GRB 260318A: Global MASTER-Net observations report
by GCN Circulars 18 Mar '26

18 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44050 SUBJECT: Fermi GRB 260318A: Global MASTER-Net observations report DATE: 26/03/18 23:00:55 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 260318A ( Fermi GBM team, GCN 44049) errorbox 572 sec after notice time and 596 sec after trigger time at 2026-03-18 22:45:44 UT, with upper limit up to 18.1 mag. The observations began at zenith distance = 62 deg. The sun altitude is -43.5 deg. The galactic latitude b = 12 deg., longitude l = 92 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3194853 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 657 | 2026-03-18 22:45:44 | MASTER-Kislovodsk | (20h 14m 11.39s , +56d 41m 32.7s) | P| | 120 | 17.6 | 797 | 2026-03-18 22:48:04 | MASTER-Kislovodsk | (20h 14m 11.18s , +56d 41m 32.8s) | P| | 120 | 17.4 | 938 | 2026-03-18 22:50:25 | MASTER-Kislovodsk | (20h 14m 11.08s , +56d 41m 36.1s) | P| | 120 | 18.1 | 1078 | 2026-03-18 22:52:45 | MASTER-Kislovodsk | (20h 14m 11.06s , +56d 41m 40.9s) | P| | 120 | 18.0 | 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/44050. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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…

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[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…

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[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…

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[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…

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[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…

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