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

[vsnet-grb-info 42190] EP260321a: Global MASTER-Net observations report
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44069 SUBJECT: EP260321a: Global MASTER-Net observations report DATE: 26/03/21 13:54:25 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) was pointed to the EP260321a ( EP Team et al., GCN 44068) errorbox 194 sec after notice time and 2105 sec after trigger time at 2026-03-21 13:05:23 UT, with upper limit up to 19.1 mag. Observations started at twilight. The observations began at zenith distance = 56 deg. The sun altitude is -16.9 deg. The galactic latitude b = 41 deg., longitude l = 239 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3200651 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 2135 | 2026-03-21 13:05:23 | MASTER-Tunka | (09h 57m 47.48s , +00d 56m 51.7s) | C | 60 | 18.8 | 2135 | 2026-03-21 13:05:23 | MASTER-Tunka | (09h 57m 34.12s , +01d 01m 05.4s) | C | 60 | 19.0 | 2208 | 2026-03-21 13:06:36 | MASTER-Tunka | (09h 57m 50.16s , +00d 58m 39.4s) | C | 60 | 18.8 | 2208 | 2026-03-21 13:06:36 | MASTER-Tunka | (09h 57m 36.78s , +01d 02m 53.3s) | C | 60 | 19.1 | 2283 | 2026-03-21 13:07:50 | MASTER-Tunka | (09h 57m 44.76s , +00d 57m 41.4s) | C | 60 | 18.9 | 2283 | 2026-03-21 13:07:50 | MASTER-Tunka | (09h 57m 31.35s , +01d 01m 55.6s) | C | 60 | 19.1 | 2354 | 2026-03-21 13:09:02 | MASTER-Tunka | (09h 57m 45.04s , +00d 58m 40.3s) | C | 60 | 18.8 | 2354 | 2026-03-21 13:09:02 | MASTER-Tunka | (09h 57m 31.61s , +01d 02m 54.6s) | C | 60 | 19.0 | 2429 | 2026-03-21 13:10:17 | MASTER-Tunka | (09h 57m 50.55s , +00d 57m 39.6s) | C | 60 | 18.8 | 2429 | 2026-03-21 13:10:17 | MASTER-Tunka | (09h 57m 37.10s , +01d 01m 53.7s) | C | 60 | 19.0 | 2502 | 2026-03-21 13:11:30 | MASTER-Tunka | (09h 57m 45.69s , +00d 56m 38.6s) | C | 60 | 18.9 | 2502 | 2026-03-21 13:11:30 | MASTER-Tunka | (09h 57m 32.22s , +01d 00m 52.6s) | C | 60 | 19.1 | 2575 | 2026-03-21 13:12:42 | MASTER-Tunka | (09h 57m 37.50s , +01d 01m 04.8s) | C | 60 | 19.1 | 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/44069. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42189] EP260321a: Einstein Probe detection of an X-ray transient
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44068 SUBJECT: EP260321a: Einstein Probe detection of an X-ray transient DATE: 26/03/21 13:01:43 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q.J. Huang (PMO, CAS), Z. C. Zou (NJU), X. Mao, D. Y. Li, H. W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260321a. The transient triggered EP-WXT (ID: 01709259023) at 2026-03-21T12:30:18 (UTC). The WXT position of the source is R.A. = 149.894 deg, DEC = 0.397 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 149.9260 deg, DEC = 0.4181 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/44068. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42188] GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44067 SUBJECT: GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations DATE: 26/03/21 11:45:32 GMT FROM: A. Brosio at ABObservatory Rosarno <antonino.brosio(a)gmail.com> A. Brosio (ABObservatory Rosarno), M. A. Tripodi (ABObservatory Rosarno), S. Savaglio (Università della Calabria), S. Benatti (INAF - Osservatorio Astronomico di Palermo), M. Basilicata, M. Rainer (INAF - Osservatorio Astronomico di Brera), S. Tosi (Università di Genova), A. Di Dato (INAF - Osservatorio Astronomico di Capodimonte), D. Liguori (Osservatorio "G. Galilei", Liceo Scientifico Cariati), A. Nastasi (GAL Hassin, Isnello), E. Pace, R. Stanga, L. Betti (Università di Firenze - Osservatorio Polifunzionale del Chianti), D. Ricci (INAF - Osservatorio Astronomico di Padova) and the NOCTIS Collaboration report: We observed the optical counterpart of GRB 260310A / AT 2026FGK, previously reported by several groups as the optical afterglow: (O'Neill et al. 2026, TNS Discovery Report 294132; Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Jayaraman et al., GCN 43994; Stein et al., GCN 43996; Martin-Carrillo et al., GCN 44000; 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; Pawar et al., GCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044; Gupta et al., GCN 44051; Salunke et al., GCN 43958; Becerra et al., GCN 44059; Volnova et al., GCN 44060; Busmann et al., GCN 44061). At JD 2461120.34019 (2026-03-20.84019 UT), we measured the source at: AT 2026FGK 18.92 +/- 0.10 Sloan r Photometric calibration was performed using the APASS catalog, adopting the comparison stars at coordinates RA(J2000) = 219.274765, Dec(J2000) = +71.914946; RA(J2000) = 219.311345, Dec(J2000) = +71.880330. View this GCN Circular online at https://gcn.nasa.gov/circulars/44067. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42187] GRB 260318A: Glowbug gamma-ray detection
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44066 SUBJECT: GRB 260318A: Glowbug gamma-ray detection DATE: 26/03/21 11:28:43 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 260318A, which was also detected by Fermi/GBM (GCN 44049), GECAM-B (GCN 44052), and SVOM/GRM (GCN 44055). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-03-18 22:35:52.696 with a duration of 7.7 s and a total significance of about 18.1 sigma. The light curve comprises two peaks at ~T0+2s and ~T0+6s. 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/44066. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42186] GRB 260310A / AT 2026fgk: KAIT optical observations
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44065 SUBJECT: GRB 260310A / AT 2026fgk: KAIT optical observations DATE: 26/03/21 06:49:53 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 251022A (Fermi GBM Team, GCN 43951; Salunke et al., GCN 43958) on March 13, 14, 18 19, 20 UT. A set of B, V, R, I and clear (roughly R) filter images were obtained. We clearly detected the optical afterglow (O'Neill et al. 2026, TNS Discovery Report 294132; Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978;Martin-Carrillo et al., GCN 43979; Méndez et al., GCN 43980;de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Jayaraman et al., GCN 43994; Stein et al., GCN 43996;Martin-Carrillo et al., GCN 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; Gupta et al., GCN 44051; Salunke et al., GCN 43958; Becerra et al., GCN 44059; Volnova et al., GCN 44060; Busmann et al., GCN 44061) in our coadd images and photometry in R band gives the following result: t-t0(d) Mag err ------------------ 3.21 17.98 0.03 4.25 18.31 0.02 8.24 18.34 0.02 9.22 18.30 0.02 10.20 18.54 0.03 View this GCN Circular online at https://gcn.nasa.gov/circulars/44065. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42185] GRB 260320A: NuSTAR detection of prompt emission
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44064 SUBJECT: GRB 260320A: NuSTAR detection of prompt emission DATE: 26/03/21 04:53:08 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260320A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-03-20 19:40:03.9 UTC, shows a detection of GRB 260320A consistent with SVOM/GRM (GCN Notices). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single bright peak lasting for ~10-s. The peak count rate is ~2000-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CdZnTe detectors. The SVOM/GRM localization (GCN Notices) at RA = 38.93, Dec = 16.64 implies an offset from the NuSTAR boresight of 92-deg (i.e. from the side of the instrument) and an offset from the geocenter of 14-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260320A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44064. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42184] GRB 260310A / AT2026fgk: NuSTAR follow-up detection
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44063 SUBJECT: GRB 260310A / AT2026fgk: NuSTAR follow-up detection DATE: 26/03/21 04:50:06 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> Elias Kammoun (Caltech), Gaurav Waratkar (Caltech), Rahul Jayaraman (Cornell), K-Ryan Hinds (Caltech), Anna Y. Q. Ho (Cornell) report: In response to our NuSTAR DDT request (PI Waratkar), NuSTAR observed the position of GRB 260310A / AT2026fgk (Fermi GBM team, GCN 43951; Arya et al., GCN 43958; Konno et al., GCN 43974; Martin-Carrillo et al., GCN 43979, 44000; Méndez et al., GCN 43980; Becerra et al., GCN 43991; Jayaraman et al., GCN 43994; 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; Rhodes et al., GCN 44005; Moskvitin et al., GCN 44006; Romanov et al., GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044; Giarratana et al., GCN 44045; Gupta et al., GCN 44051; Ho et al., GCN 44057; Passaleva et al., GCN 44058; Becerra et al., GCN 44059; Volnova et al., GCN 44060), beginning at 2026-03-20T17:20:02 UTC with an exposure time of 7523 s. We performed a preliminary analysis of the NuSTAR spectrum in the 3-79 keV energy range from both the FPMA and FPMB modules by fitting an absorbed power law. We find a photon index of 1.76 ± 0.22 with an unabsorbed flux of (1.16 ± 0.15) x 10^-12 ergs/cm2/s (2-10 keV). All the uncertainties are 90% CL. At the reported redshift of 0.153 (Ugarte Postigo et al., GCN 43984; Hinds et al., GCN 43977), this would correspond to a luminosity (2-10 keV) of (7.2 ± 0.7) x 10^43 erg/s. We thank the entire NuSTAR Science & Mission operations teams for the rapid approval and execution of this DDT observation. NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44063. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42183] EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44062 SUBJECT: EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare DATE: 26/03/21 03:19:15 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, automatically responded to the EP-WXT trigger 01709258989 (Zhou et al. GCN 44054) starting at 04:57 UT, about 2.4 hours after the trigger. A set of clear (roughly R) filter images were obtained and lasted for ~2.5 hours. Photometry on the suggested flare star 1RXS J073101.9+460030 (confirmed by Perez-Garcia et al., GCN 44056) show that its brightness remain around 12.5 mag for about 1 hour, then another flare started at 06:05 UT (3.53 hours after trigger), brightened to ~12.0 mag at peak time of 06:11 UT, then decreased to ~12.4 mag around 06:23 UT. This confirming the EP X-ray trigger is related to the stellar flare. View this GCN Circular online at https://gcn.nasa.gov/circulars/44062. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42182] GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
by GCN Circulars 21 Mar '26

21 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44061 SUBJECT: GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening DATE: 26/03/21 01:42:34 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann, Daniel Gruen (LMU), Xander J. Hall, Brendan O'Connor, Antonella Palmese (CMU) report: We observed the optical/NIR counterpart of GRB 260310A (Fermi GBM team, GCN 43951; Salunke et al., GCN 43958), AT 2026fgk (e.g. O'Neill et al. 2026, TNS Discovery Report 294132; Konno et al., GCN 43974; Hinds et al., GCN 43977), with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the g, r, i, z, J, and Ks band starting at 2026-03-19T23:22:38 (9.77 days after the GRB trigger) and 2026-03-20T22:36:22 (10.74 after the GRB trigger). Unlike suggested by Becerra et al. (CGN 44059) we do not see signs of rebrightening in our observations in any filter (see also Volnova et al., GCN 44060). We thank Michael Schmidt and Silona Wilke for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44061. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42181] GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
by GCN Circulars 20 Mar '26

20 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44060 SUBJECT: GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy DATE: 26/03/20 22:31:46 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> A. Volnova (IKI), N. Pankov (IKI), E. Klunko (ISTP), A. S. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI) report on behalf of GRB IKI FuN. We observed the field of GRB260310A/AT2026fgk detected by Fermi/GBM (Fermi GBM team, GCN 43951) and AstroSat(Salunke et al., GCN 43958) with AZT-33IK telescope of Mondy observatory. We obtained series in B and R filters starting on 2026-03-13. The OT discovered by GOTO (O'Neill et al. 2026, TNS Discovery Report 294132) and observed earlier (Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978;Martin-Carrillo et al., GCN 43979; Méndez et al., GCN 43980;de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Jayaraman et al., GCN 43994; Stein et al., GCN 43996;Martin-Carrillo et al., GCN 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; Gupta et al., GCN 44051) is clearly detected in our images. Preliminary PSF photometry on some epochs is the following Date UT_start t_mid - T0, filter exp, mag err UL(3sigma) days s 2026-03-15 15:09:04 5.43535 15*120 B 19.18 0.05 23.0 2026-03-16 14:37:32 6.41345 15*120 B 19.05 0.05 22.6 2026-03-17 18:59:03 7.60549 30*120 B 19.18 0.05 22.7 2026-03-18 18:40:29 8.58565 19*120 B 19.47 0.06 21.7 2026-03-19 18:09:48 9.57128 30*120 B 19.61 0.06 23.2 2026-03-15 14:48:55 5.52493 11*120 R 18.27 0.05 23.0 2026-03-16 14:07:40 6.39202 13*120 R 18.22 0.05 22.8 2026-03-17 18:22:13 7.56948 15*120 R 18.29 0.06 22.8 2026-03-18 18:06:29 8.55786 15*120 R 18.60 0.06 22.4 2026-03-19 19:11:16 9.60355 15*120 R 18.71 0.07 22.7 The photometry is based on the nearby calibrations stars of PS1 catalogue converted to B, R using the Lupton (2005) transformations. The magnitudes are not corrected for Galactic extinctions. We do not observe the rebrightening reported in COLIBRÍ observations (Becerra et al., GCN 44059) up to the latest epoch (~9.6 days) in B,R - filters. Based on classification of the progenitor (Atteia et al., GCN 43981; Minaev et al., GCN 44053) we urge follow up observations to search for a supernova associated with GRB 260310A. View this GCN Circular online at https://gcn.nasa.gov/circulars/44060. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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