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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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[vsnet-grb-info 42950] GRB 260603A: Simeiz Zeiss-1000 optical upper limit
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44819 SUBJECT: GRB 260603A: Simeiz Zeiss-1000 optical upper limit DATE: 26/06/04 09:46:23 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Pozanenko (IKI), A. Novichonok (KIAM), A. Volnova (IKI) report on behalf of IKI-GRB-FuN We observed the field of GRB 260603A (Zhao et al., GCN 44787; Li et al., GCN 44805) with the Zeiss-1000 1-meter telescope of Simeiz Observatory starting on 2026-06-03 UT 19:38:36 (~0.6 days since trigger). A series of 20x180 sec exposures was acquired in the R-filter using a CCD-photometer. We do not detect the optical afterglow (Guelfand et al., GCN 44791, 44797; Li et al., GCN 44799; Freeberg et al., GCN 44800). The preliminary upper limit and the observation details are summarized below: Date UTstart t-T0 Exp. Filter Mag Err. UL (mid,days) (n*s) (3-sigma) 2026-06-03 19:38:36 0.60443 20*180 R n/d n/d 22.3 The photometry is based on nearby USNO-B1.0 stars and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44819. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42949] GRB 260604B: Fermi GBM Final Real-time Localization
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44818 SUBJECT: GRB 260604B: Fermi GBM Final Real-time Localization DATE: 26/06/04 08:58:18 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 SHORT GRB At 08:45:55 UT on 4 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260604B (trigger 802255560.356374 / 260604365). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 173.4, Dec = -19.9 (J2000 degrees, equivalent to J2000 11h 33m, -19d 53'), with a statistical uncertainty of 10.8 degrees. The angle from the Fermi LAT boresight is 60.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604365/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604365/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604365/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44818. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42948] GRB 260601A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44817 SUBJECT: GRB 260601A: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/04 08:23:39 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected the short GRB 260601A at 11:00:12.042 UTC on 1 June 2026 (trigger #1464346716; https://cgbm.calet.jp/cgbm_trigger/flight/1464346716/index.html) A CGBM Notice was distributed in near real time. This event was also reported by Fermi GBM (The Fermi GBM team, GCN #44755; Holzmann Airasca et al., GCN #44760), Glowbug (Cheung et al., GCN #44763), GECAM-B (Wang et al., GCN #44778), SVOM/GRM (Wang et al., GCN #44793), and KONUS-Wind (IPN_RAW Notice at 2026-06-01 11:00:09.16 UTC). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure, starting at T+0.40 s, peaking at T+0.50 s, and ending at T+0.59 s. The T90 and T50 durations measured with the SGM data are 0.18 +/- 0.01 s and 0.05 +/- 0.03 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1464346716/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44817. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42947] EP260602a: EP-FXT follow-up observation
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44816 SUBJECT: EP260602a: EP-FXT follow-up observation DATE: 26/06/04 07:09:04 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Z. X. Li, G. L. Huang, J. Y. Cao (IHEP, CAS), Y. Wang (PMO, CAS; UCB), G. J. Yang, W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260602a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Li et al., GCN 44770) at 2026-06-02T08:11:20 (UTC). Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-03T14:02:47(UTC), ~30 hours after the WXT detection. The exposure time of the observation is around 6 ks. The on-ground analysis of the FXT B data found an uncatalogued source at R.A. = 240.8343 deg, DEC = 50.4636 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is approximately consistent with the position of the optical counterpart (Xu et al., GCN 44781; Watson et al., GCN 44790; Malesani et al., GCN 44807). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.03×10^20 cm^-2, and a photon index of 1.6 (-0.9, +1.2). The derived average unabsorbed 0.5-10 keV flux is 7.1 (-4.3, +13.0) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 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/44816. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42946] EP260603a: Global MASTER-Net observations report
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44815 SUBJECT: EP260603a: Global MASTER-Net observations report DATE: 26/06/04 06:18:16 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-OAGH robotic telescope [1] located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the EP260603a ( EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> et al., GCN 44814) errorbox 436 sec after notice time and 43770 sec after trigger time at 2026-06-04 06:00:42 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 58 deg. The sun altitude is -33.4 deg. The galactic latitude b = 25 deg., longitude l = 340 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3359661 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 43860 | 2026-06-04 06:00:42 | MASTER-OAGH | (15h 18m 40.19s , -26d 59m 12.9s) | C | 180 | 17.9 | 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/44815. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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