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[vsnet-grb-info 42960] EP260602b: J-band upper limit with WINTER
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44829 SUBJECT: EP260602b: J-band upper limit with WINTER DATE: 26/06/05 01:18:25 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Tanishk Mohan (IITB), Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (NOIRLab), Benjamin Schneider (LAM), Robert Stein (UMD), Viraj Karambelkar (Columbia), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of EP260602b (Wu et al., GCN 44786; Wu et al., GCN 44802) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2026-06-03T04:53:16 UTC in the J band (~11 hr after the EP trigger), consisting of 15*120 sec exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) We do not detect a source at the optical counterpart location (He et al., GCN 44780; Eyles-Ferris et al., GCN 44809; Bochenek et al., GCN 44811). We obtain the following 5-sigma upper limit: J = 19.1 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/44829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42959] GRB 260604C: LAST detection of optical counterpart candidate
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44828 SUBJECT: GRB 260604C: LAST detection of optical counterpart candidate DATE: 26/06/04 23:52:38 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. We report observations of GRB 260604C, detected by Fermi-GBM (Fermi GBM team, GCN 44822) and SVOM (Gotz et al, GCN 44823). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002). Observations of GRB 260604C were taken over 4 sequential epochs in clear band (similar to the Gaia Bp band). The first epoch began at 2026-06-04 20:35:04 UTC (T-T0 = 0.275 h). Each epoch consists of 20x20s exposures per telescope. We detect one credible optical transient within the field reported by SVOM (Gotz et al, GCN 44823) consistent with the position of AT 2026ofi (TNS Report No. 307026) reported by MASTER (Lipunov et al, GCN 44827). The transient is well detected within each epoch and shows a rapid decay, consistent with afterglow emission. | Tmid-T0 (h) | Mag (AB) | | ------------ | ----------- | | 0.33 | 17.12 | | 0.45 | 16.85 | | 0.57 | 16.63 | | 0.75 | 16.42 | Previous observations of the field yield no detections on the source positions up to 2026-06-01 20:46:47 UTC (T0-T = 3d) with a 5-sigma limiting magnitude of 20.15 (AB). We encourage further follow-up observations. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42958] GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44827 SUBJECT: GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery DATE: 26/06/04 22:45:21 GMT FROM: Vladimir Lipunov at Lomonosov Moscow State University <lipunov(a)sai.msu.ru> MASTER OT J145749.59+284903.0 discovery MASTER-Tavrida auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 14h 57m 49.59s +28d 49m 03.0s on 2026-06-04.86020 UT. The OT magnitude (unfiltered) is 17.5m at04.86020UT (mlim=19.4). The OT is seen in 14 images. There is no minor planet at this place. We have reference image on 2020-09-17.71399 UT with unfiltered mlim= 18.1m. Spectral observations are required. View this GCN Circular online at https://gcn.nasa.gov/circulars/44827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42957] Fermi GRB 260604C: Global MASTER-Net observations report
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44826 SUBJECT: Fermi GRB 260604C: Global MASTER-Net observations report DATE: 26/06/04 21:20:24 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), M. Segura, 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-Tavrida robotic telescope [1] located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 260604C ( Fermi GBM team, GCN 44822) errorbox 68 sec after notice time and 121 sec after trigger time at 2026-06-04 20:20:45 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 13 deg. The sun altitude is -20.4 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260604C errorbox 2607 sec after notice time and 2660 sec after trigger time at 2026-06-04 21:03:04 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 28 deg. The sun altitude is -23.8 deg. The galactic latitude b = 65 deg., longitude l = 54 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3361051 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 132 | 2026-06-04 20:20:45 | MASTER-Tavrida | (14h 45m 39.13s , +34d 23m 10.1s) | C | 20 | 18.2 | 159 | 2026-06-04 20:21:08 | MASTER-Tavrida | (14h 45m 39.22s , +34d 23m 08.2s) | C | 30 | 18.5 | 201 | 2026-06-04 20:21:45 | MASTER-Tavrida | (14h 45m 39.31s , +34d 23m 05.7s) | C | 40 | 18.7 | 244 | 2026-06-04 20:22:28 | MASTER-Tavrida | (14h 45m 39.40s , +34d 23m 03.5s) | C | 40 | 18.7 | 292 | 2026-06-04 20:23:11 | MASTER-Tavrida | (14h 45m 39.48s , +34d 23m 00.9s) | C | 50 | 18.9 | 351 | 2026-06-04 20:24:05 | MASTER-Tavrida | (14h 45m 39.57s , +34d 22m 58.3s) | C | 60 | 19.0 | 424 | 2026-06-04 20:25:08 | MASTER-Tavrida | (14h 45m 39.70s , +34d 22m 55.4s) | C | 80 | 19.9 | 512 | 2026-06-04 20:26:31 | MASTER-Tavrida | (14h 45m 39.83s , +34d 22m 52.2s) | C | 90 | 18.1 | 616 | 2026-06-04 20:28:05 | MASTER-Tavrida | (14h 45m 39.93s , +34d 22m 49.5s) | C | 110 | 18.8 | 753 | 2026-06-04 20:30:17 | MASTER-Tavrida | (14h 41m 46.90s , +33d 53m 19.6s) | C | 120 | 19.3 | 2690 | 2026-06-04 21:03:04 | MASTER-Kislovodsk | (14h 31m 34.56s , +34d 00m 31.5s) | C | 60 | 18.4 | 2780 | 2026-06-04 21:04:34 | MASTER-Kislovodsk | (14h 41m 05.21s , +33d 59m 44.5s) | C | 60 | 18.5 | 2868 | 2026-06-04 21:06:02 | MASTER-Kislovodsk | (14h 36m 52.22s , +35d 55m 19.9s) | C | 60 | 18.3 | 2957 | 2026-06-04 21:07:31 | MASTER-Kislovodsk | (14h 46m 41.72s , +35d 54m 08.3s) | C | 60 | 18.4 | 3046 | 2026-06-04 21:09:00 | MASTER-Kislovodsk | (14h 45m 53.08s , +34d 00m 34.0s) | C | 60 | 18.5 | 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/44826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42956] Fermi GRB 260604C: Global MASTER-Net observations report
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44825 SUBJECT: Fermi GRB 260604C: Global MASTER-Net observations report DATE: 26/06/04 21:18:02 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), M. Segura, 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-Tavrida robotic telescope [1] located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 260604C ( Fermi GBM team, GCN 44822) errorbox 68 sec after notice time and 121 sec after trigger time at 2026-06-04 20:20:45 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 13 deg. The sun altitude is -20.4 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260604C errorbox 2607 sec after notice time and 2660 sec after trigger time at 2026-06-04 21:03:04 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 28 deg. The sun altitude is -23.8 deg. The galactic latitude b = 65 deg., longitude l = 54 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3361051 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 132 | 2026-06-04 20:20:45 | MASTER-Tavrida | (14h 45m 39.13s , +34d 23m 10.1s) | C | 20 | 18.2 | 159 | 2026-06-04 20:21:08 | MASTER-Tavrida | (14h 45m 39.22s , +34d 23m 08.2s) | C | 30 | 18.5 | 201 | 2026-06-04 20:21:45 | MASTER-Tavrida | (14h 45m 39.31s , +34d 23m 05.7s) | C | 40 | 18.7 | 244 | 2026-06-04 20:22:28 | MASTER-Tavrida | (14h 45m 39.40s , +34d 23m 03.5s) | C | 40 | 18.7 | 292 | 2026-06-04 20:23:11 | MASTER-Tavrida | (14h 45m 39.48s , +34d 23m 00.9s) | C | 50 | 18.9 | 351 | 2026-06-04 20:24:05 | MASTER-Tavrida | (14h 45m 39.57s , +34d 22m 58.3s) | C | 60 | 19.0 | 424 | 2026-06-04 20:25:08 | MASTER-Tavrida | (14h 45m 39.70s , +34d 22m 55.4s) | C | 80 | 19.9 | 512 | 2026-06-04 20:26:31 | MASTER-Tavrida | (14h 45m 39.83s , +34d 22m 52.2s) | C | 90 | 18.1 | 616 | 2026-06-04 20:28:05 | MASTER-Tavrida | (14h 45m 39.93s , +34d 22m 49.5s) | C | 110 | 18.8 | 753 | 2026-06-04 20:30:17 | MASTER-Tavrida | (14h 41m 46.90s , +33d 53m 19.6s) | C | 120 | 19.3 | 2690 | 2026-06-04 21:03:04 | MASTER-Kislovodsk | (14h 31m 34.56s , +34d 00m 31.5s) | C | 60 | 18.4 | 2780 | 2026-06-04 21:04:34 | MASTER-Kislovodsk | (14h 41m 05.21s , +33d 59m 44.5s) | C | 60 | 18.5 | 2868 | 2026-06-04 21:06:02 | MASTER-Kislovodsk | (14h 36m 52.22s , +35d 55m 19.9s) | C | 60 | 18.3 | 2957 | 2026-06-04 21:07:31 | MASTER-Kislovodsk | (14h 46m 41.72s , +35d 54m 08.3s) | C | 60 | 18.4 | 3046 | 2026-06-04 21:09:00 | MASTER-Kislovodsk | (14h 45m 53.08s , +34d 00m 34.0s) | C | 60 | 18.5 | 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/44825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42955] SVOM GRB260604.85: Global MASTER-Net observations report
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44824 SUBJECT: SVOM GRB260604.85: Global MASTER-Net observations report DATE: 26/06/04 20:48:54 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), M. Segura, 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-Tavrida robotic telescope [1] located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the SVOM GRB260604.85 (trigger No 1780604437,14h 57m 12.77s , +28d 36m 26.6s, R=0.1738) errorbox 43 sec after notice time and 713 sec after trigger time at 2026-06-04 20:32:30 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 18 deg. The sun altitude is -21.0 deg. The galactic latitude b = 62 deg., longitude l = 43 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3361056 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 774 | 2026-06-04 20:32:30 | MASTER-Tavrida | (14h 57m 09.62s , +29d 05m 58.4s) | C | 120 | 19.4 | 897 | 2026-06-04 20:34:33 | MASTER-Tavrida | (14h 57m 09.73s , +29d 05m 54.0s) | C | 120 | 19.4 | 1019 | 2026-06-04 20:36:36 | MASTER-Tavrida | (14h 57m 09.83s , +29d 05m 50.2s) | C | 120 | 19.4 | 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/44824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42954] GRB 260604C: SVOM detection of a long burst
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44823 SUBJECT: GRB 260604C: SVOM detection of a long burst DATE: 26/06/04 20:43:09 GMT FROM: Diego Gotz at CEA <diego.gotz(a)cea.fr> D. Gotz, D. Adrien, N. Dagoneau, S. Bisero (CEA Saclay) report on behalf of the SVOM mission team: At 2026-06-04T20:21:59 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260604C (SVOM burst-id sb26060404). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 4 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.23 in the [5-20] keV energy band over a time window of 163.84 seconds starting at 2026-06-04T20:19:56 UTC. The localization of the best alert is R.A., Dec. 224.3461, 28.6558 degrees: R.A. (J2000) = 14h57m23s Dec. (J2000) = 28d39m20s with a 90% confidence level (C.L.) radius of 9.6 arcmin (including systematic error of 2 arcmin added in quadrature). This position is compatible with the GRB detected by Fermi/GBM GCN 44822 . SVOM slewed to the burst position. No X-ray observation could be performed by SVOM/MXT for the time being. Optical observations by VT will be published in a further circular. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Sofia Bisero: sofia.bisero(a)cea.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42953] GRB 260604C: Fermi GBM Final Real-time Localization
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44822 SUBJECT: GRB 260604C: Fermi GBM Final Real-time Localization DATE: 26/06/04 20:31:01 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 20:18:44 UT on 4 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260604C (trigger 802297129.411688 / 260604846). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 220.5, Dec = 33.4 (J2000 degrees, equivalent to J2000 14h 41m, 33d 23'), with a statistical uncertainty of 1.0 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/bn260604846/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604846/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604846/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42952] GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44821 SUBJECT: GRB 260515A: SVOM/VT optical detection at about 18 days post trigger DATE: 26/06/04 15:44:09 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio, A. Saccardi and D. Gotz (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed further ToO observations of GRB260515A triggered by SVOM/ECLAIRs (sb26051504, Brunet et al., GCN 44622, GCN 44666). The burst was also detected by Konus-Wind (Frederiks et al., GCN 44647). The observation started at 2026-06-03T02:02:18 UTC, i.e., 18.28 days post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The counterpart (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626; Lipunov et al., GCN 44627; Wu et al., GCN 44628; Dennefeld et al., GCN 44633; Li et al., GCN 44634; Wang et al., GCN 44642; Antier et al., GCN 44643; Pérez-Fournon et al., GCN 44645; Dimple et al. GCN 44646; Moskvitin et al., GCN 44652; Bochenek et al., GCN 44658) with redshift z=0.764 (Malesani et al., GCN 44629) was faintly detected VT_R. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 18.38 d VT_R 108*70 s 23.5 +/- 0.3 mag 18.38 d VT_B 110*70 s >24.0 mag (3 sigma upper limit) 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/44821. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42951] GRB 260603A: NOT optical observations
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44820 SUBJECT: GRB 260603A: NOT optical observations DATE: 26/06/04 12:05:46 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF/OACN and DARK/NBI), G. Corcoran (UCD), A. Martin-Carrillo (UCD), N. Pyykkinen (NOT), A. S. Mårtensson (NOT) report on behalf of a larger collaboration: We observed the optical afterglow (Guelfand et al., GCNs 44791, 44797; Li et al., GCN 44799) of the SVOM GRB 260603A (Zhao et al., GCN 44787) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the SDSS r band. The optical afterglow is detected with an AB magnitude r = 23.27 +- 0.21, at a mean epoch of Jun 4.02 UT (0.786 days after trigger). This magnitude is calibrated against nearby stars from the Pan-STARRS catalog, and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44820. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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