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

[vsnet-grb-info 43499] IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 04 Aug '26

04 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45282 SUBJECT: IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/08/04 05:10:36 GMT FROM: Sam Hori at IceCube/U Wisc-Madison <sahori(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-Cascade 260801A (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/142940_41461633.amon) in a time range of 1000 seconds centered on the alert event time (2026-08-01 17:21:57.369 UTC to 2026-08-01 17:38:37.369 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-Cascade 260801A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 1.3e-01 to 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-Cascade 260801A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-07-31 17:30:17.369 UTC to 2026-08-02 17:30:17.369 UTC). In this case, we report a p-value of 0.75, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 1.5e-01 to 1.7e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-Cascade 260801A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/45282. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43498] GRB 260804A: Fermi GBM Final Real-time Localization
by GCN Circulars 04 Aug '26

04 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45281 SUBJECT: GRB 260804A: Fermi GBM Final Real-time Localization DATE: 26/08/04 03:17:28 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 03:07:09 UT on 4 Aug 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260804A (trigger 807505634.188604 / 260804130). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 93.8, Dec = 18.0 (J2000 degrees, equivalent to J2000 06h 15m, 18d 00'), with a statistical uncertainty of 3.6 degrees. The angle from the Fermi LAT boresight is 74.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260804130/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260804130/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260804130/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45281. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43497] GRB 260708A: LCO further optical observations show supernova features
by GCN Circulars 04 Aug '26

04 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45280 SUBJECT: GRB 260708A: LCO further optical observations show supernova features DATE: 26/08/04 02:02:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y.Y. Shi (GXU), C. Wu, L.P. Xin (NAOC), A. Saccardi, D. Turpin (CEA/Irfu), Y.X. Guan, S.J. Yin (GXU) report on behalf of the SVOM mission team: We have continued monitoring the optical counterpart (Shilova et al., GCN 45123; Freeberg et al., GCN 45127; Sheng et al., GCN 45147) of the Fermi long GRB 260708A (Fermi/GBM Team, GCN 45115; Fermi-LAT, Holzmann Airasca et al., GCN 45117), using SINISTRO instruments mounted on 1-m telescopes of the LCO global network. We observed the optical counterpart in imaging using the g, r, i bands from 2026-07-11 (3.56 days after the trigger) to 2026-08-02 (25.03 days after the trigger). The optical counterpart shows a color change toward blue. It was measured to have a brightness of g=19.56+/-0.02 mag at 3.56 days post-trigger and g=18.88+/-0.02 mag at 11.48 days respectively, which show a rebrightening of the counterpart with a rise time of ~11.5 days post-trigger. Photometry was calibrated against the UCAC4 catalog, without template subtraction and not corrected for Galactic extinction. We suggest that it is likely the supernova associated with the burst. Multi-band photometric and spectroscopic observations are encouraged. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/45280. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43496] GRB 260803A: Fermi GBM Final Real-time Localization
by GCN Circulars 03 Aug '26

03 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45279 SUBJECT: GRB 260803A: Fermi GBM Final Real-time Localization DATE: 26/08/03 17:39:21 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 17:28:46 UT on 3 Aug 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260803A (trigger 807470931.896978 / 260803728). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 22.1, Dec = 68.7 (J2000 degrees, equivalent to J2000 01h 28m, 68d 42'), with a statistical uncertainty of 6.7 degrees. The angle from the Fermi LAT boresight is 74.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260803728/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260803728/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260803728/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45279. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43495] Fermi GRB 260802B: Global MASTER-Net observations report
by GCN Circulars 03 Aug '26

03 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45278 SUBJECT: Fermi GRB 260802B: Global MASTER-Net observations report DATE: 26/08/03 06:45:36 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-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260802B ( Fermi GBM team, GCN 45273) errorbox 37429 sec after notice time and 37470 sec after trigger time at 2026-08-02 19:24:19 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 23 deg. The sun altitude is -43.4 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260802B errorbox 71774 sec after notice time and 71815 sec after trigger time at 2026-08-03 04:56:44 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 7 deg. The sun altitude is -75.4 deg. The galactic latitude b = -36 deg., longitude l = 29 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3454222 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 37501 | 2026-08-02 19:24:19 | MASTER-SAAO | (19h 17m 14.20s , -42d 47m 11.3s) | C | 60 | 19.5 | 37561 | 2026-08-02 19:24:19 | MASTER-SAAO | (19h 17m 14.20s , -42d 47m 11.3s) | C | 180 | 20.0 | Coadd 38459 | 2026-08-02 19:40:17 | MASTER-SAAO | (19h 17m 07.08s , -42d 45m 56.4s) | C | 60 | 19.4 | 40530 | 2026-08-02 20:14:48 | MASTER-SAAO | (19h 17m 05.30s , -42d 45m 20.8s) | C | 60 | 19.2 | 40590 | 2026-08-02 20:14:48 | MASTER-SAAO | (19h 17m 05.30s , -42d 45m 20.8s) | C | 180 | 19.8 | Coadd 42524 | 2026-08-02 20:48:02 | MASTER-SAAO | (19h 17m 02.10s , -42d 44m 39.2s) | C | 60 | 19.1 | 71846 | 2026-08-03 04:56:44 | MASTER-OAFA | (21h 18m 53.41s , -38d 46m 40.4s) | C | 60 | 19.8 | 71906 | 2026-08-03 04:56:44 | MASTER-OAFA | (21h 18m 53.42s , -38d 46m 40.4s) | C | 180 | 20.5 | Coadd 71922 | 2026-08-03 04:57:59 | MASTER-OAFA | (21h 29m 08.59s , -38d 46m 12.0s) | C | 60 | 19.6 | 71982 | 2026-08-03 04:57:59 | MASTER-OAFA | (21h 29m 08.59s , -38d 46m 12.0s) | C | 180 | 19.9 | Coadd 71998 | 2026-08-03 04:59:16 | MASTER-OAFA | (21h 29m 15.65s , -38d 47m 09.5s) | C | 60 | 18.1 | 72074 | 2026-08-03 05:00:31 | MASTER-OAFA | (21h 29m 09.99s , -38d 48m 07.2s) | C | 60 | 19.6 | 72151 | 2026-08-03 05:01:49 | MASTER-OAFA | (21h 29m 15.95s , -38d 47m 37.3s) | C | 60 | 19.6 | 72211 | 2026-08-03 05:01:49 | MASTER-OAFA | (21h 29m 15.94s , -38d 47m 37.4s) | C | 180 | 20.3 | Coadd 72227 | 2026-08-03 05:03:05 | MASTER-OAFA | (21h 29m 12.55s , -38d 46m 02.4s) | C | 60 | 19.8 | 72304 | 2026-08-03 05:04:22 | MASTER-OAFA | (21h 18m 58.01s , -38d 47m 19.2s) | C | 60 | 19.8 | 72380 | 2026-08-03 05:05:38 | MASTER-OAFA | (21h 29m 16.11s , -38d 46m 21.1s) | C | 60 | 19.8 | 72458 | 2026-08-03 05:06:56 | MASTER-OAFA | (21h 18m 55.88s , -38d 46m 20.1s) | C | 60 | 19.8 | 72778 | 2026-08-03 05:12:16 | MASTER-OAFA | (21h 14m 35.17s , -40d 40m 47.0s) | C | 60 | 19.5 | 72838 | 2026-08-03 05:12:16 | MASTER-OAFA | (21h 14m 35.17s , -40d 40m 47.0s) | C | 180 | 20.2 | Coadd 72854 | 2026-08-03 05:13:32 | MASTER-OAFA | (21h 25m 10.51s , -40d 39m 41.0s) | C | 60 | 19.6 | 72914 | 2026-08-03 05:13:32 | MASTER-OAFA | (21h 25m 10.51s , -40d 39m 41.0s) | C | 180 | 20.4 | Coadd 72929 | 2026-08-03 05:14:47 | MASTER-OAFA | (21h 25m 04.54s , -40d 40m 32.6s) | C | 60 | 19.8 | 73007 | 2026-08-03 05:16:04 | MASTER-OAFA | (21h 25m 04.71s , -40d 39m 30.2s) | C | 60 | 19.7 | 73084 | 2026-08-03 05:17:22 | MASTER-OAFA | (21h 14m 39.13s , -40d 39m 54.5s) | C | 60 | 19.3 | 73159 | 2026-08-03 05:18:37 | MASTER-OAFA | (21h 14m 32.10s , -40d 40m 51.7s) | C | 60 | 19.5 | 73237 | 2026-08-03 05:19:55 | MASTER-OAFA | (21h 14m 39.11s , -40d 40m 21.5s) | C | 60 | 19.6 | 73315 | 2026-08-03 05:21:13 | MASTER-OAFA | (21h 25m 08.28s , -40d 39m 48.9s) | C | 60 | 19.5 | 73392 | 2026-08-03 05:22:30 | MASTER-OAFA | (21h 14m 36.58s , -40d 40m 20.7s) | C | 60 | 19.5 | 73866 | 2026-08-03 05:30:24 | MASTER-OAFA | (21h 34m 38.32s , -40d 40m 07.8s) | C | 60 | 19.7 | 73926 | 2026-08-03 05:30:24 | MASTER-OAFA | (21h 34m 38.32s , -40d 40m 07.8s) | C | 180 | 20.2 | Coadd 73941 | 2026-08-03 05:31:39 | MASTER-OAFA | (21h 45m 10.46s , -40d 41m 41.8s) | C | 60 | 19.6 | 74001 | 2026-08-03 05:31:39 | MASTER-OAFA | (21h 45m 10.46s , -40d 41m 41.7s) | C | 180 | 20.0 | Coadd 74020 | 2026-08-03 05:32:57 | MASTER-OAFA | (21h 45m 14.27s , -40d 40m 20.0s) | C | 60 | 19.3 | 74096 | 2026-08-03 05:34:14 | MASTER-OAFA | (21h 45m 07.90s , -40d 41m 03.5s) | C | 60 | 19.2 | 74171 | 2026-08-03 05:35:29 | MASTER-OAFA | (21h 45m 07.02s , -40d 40m 01.0s) | C | 60 | 19.4 | 74231 | 2026-08-03 05:35:29 | MASTER-OAFA | (21h 45m 07.02s , -40d 40m 01.0s) | C | 180 | 20.0 | Coadd 74248 | 2026-08-03 05:36:46 | MASTER-OAFA | (21h 45m 13.98s , -40d 40m 59.3s) | C | 60 | 19.2 | 74326 | 2026-08-03 05:38:04 | MASTER-OAFA | (21h 34m 36.09s , -40d 41m 24.7s) | C | 60 | 19.5 | 74403 | 2026-08-03 05:39:21 | MASTER-OAFA | (21h 45m 15.08s , -40d 41m 26.3s) | C | 60 | 19.6 | 74479 | 2026-08-03 05:40:37 | MASTER-OAFA | (21h 34m 39.72s , -40d 39m 28.3s) | C | 60 | 19.5 | 74555 | 2026-08-03 05:41:53 | MASTER-OAFA | (21h 29m 17.38s , -38d 46m 43.4s) | C | 60 | 19.0 | 74629 | 2026-08-03 05:43:07 | MASTER-OAFA | (21h 29m 21.21s , -38d 45m 08.4s) | C | 60 | 19.2 | 75908 | 2026-08-03 06:04:25 | MASTER-OAFA | (22h 56m 32.11s , -11d 47m 43.6s) | C | 60 | 19.0 | 75968 | 2026-08-03 06:04:25 | MASTER-OAFA | (22h 56m 32.11s , -11d 47m 43.6s) | C | 180 | 19.6 | Coadd 75981 | 2026-08-03 06:05:39 | MASTER-OAFA | (22h 56m 37.44s , -11d 48m 44.6s) | C | 60 | 18.9 | 76059 | 2026-08-03 06:06:57 | MASTER-OAFA | (22h 56m 30.45s , -11d 49m 45.7s) | C | 60 | 18.9 | 76164 | 2026-08-03 06:08:12 | MASTER-OAFA | (22h 56m 37.17s , -11d 49m 41.0s) | C | 120 | 19.3 | 76284 | 2026-08-03 06:08:12 | MASTER-OAFA | (22h 56m 37.17s , -11d 49m 41.0s) | C | 360 | 19.8 | Coadd 76301 | 2026-08-03 06:10:29 | MASTER-OAFA | (22h 56m 34.06s , -11d 48m 12.0s) | C | 120 | 18.9 | 76439 | 2026-08-03 06:12:47 | MASTER-OAFA | (22h 56m 33.86s , -11d 49m 44.5s) | C | 120 | 18.8 | 76574 | 2026-08-03 06:15:02 | MASTER-OAFA | (22h 56m 36.54s , -11d 48m 15.0s) | C | 120 | 18.9 | 76694 | 2026-08-03 06:15:02 | MASTER-OAFA | (22h 56m 36.54s , -11d 48m 15.1s) | C | 360 | 19.6 | Coadd 76713 | 2026-08-03 06:17:21 | MASTER-OAFA | (22h 56m 29.81s , -11d 48m 59.0s) | C | 120 | 19.0 | 76850 | 2026-08-03 06:19:38 | MASTER-OAFA | (22h 56m 30.26s , -11d 48m 02.5s) | C | 120 | 18.9 | 76964 | 2026-08-03 06:22:02 | MASTER-OAFA | (20h 52m 21.01s , -18d 34m 06.6s) | C | 60 | 17.8 | 77024 | 2026-08-03 06:22:02 | MASTER-OAFA | (20h 52m 21.01s , -18d 34m 06.6s) | C | 180 | 17.2 | Coadd 77038 | 2026-08-03 06:23:16 | MASTER-OAFA | (20h 52m 14.06s , -18d 35m 09.0s) | C | 60 | 16.3 | 77116 | 2026-08-03 06:24:34 | MASTER-OAFA | (20h 52m 20.49s , -18d 35m 03.7s) | C | 60 | 13.6 | 77223 | 2026-08-03 06:25:51 | MASTER-OAFA | (20h 52m 17.12s , -18d 33m 47.2s) | C | 120 | 18.4 | 77343 | 2026-08-03 06:25:51 | MASTER-OAFA | (20h 52m 17.13s , -18d 33m 47.2s) | C | 360 | 19.7 | Coadd 77361 | 2026-08-03 06:28:08 | MASTER-OAFA | (20h 52m 17.05s , -18d 34m 58.9s) | C | 120 | 19.2 | 77497 | 2026-08-03 06:30:25 | MASTER-OAFA | (20h 52m 20.90s , -18d 33m 30.0s) | C | 120 | 19.6 | 77682 | 2026-08-03 06:33:29 | MASTER-OAFA | (20h 52m 35.71s , -18d 32m 24.3s) | C | 120 | 19.7 | 77817 | 2026-08-03 06:35:44 | MASTER-OAFA | (20h 52m 36.79s , -18d 31m 22.2s) | C | 120 | 19.3 | 77954 | 2026-08-03 06:38:02 | MASTER-OAFA | (20h 52m 42.22s , -18d 32m 20.9s) | C | 120 | 18.9 | 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/45278. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43494] GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
by GCN Circulars 03 Aug '26

03 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45277 SUBJECT: GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation DATE: 26/08/03 04:01:00 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.H. Cheng (YNU), Y.H. Jiang (NJU), D. Zhu (YNU) , H.Y. Liu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of GRB 260802A detected by SVOM/ECLAIRs (Feng et al., GCN 45270). The observation started at 2026-08-02 13:02:30 (UTC), about 3.65 hr after the SVOM trigger, with a total exposure time of around 3 ks. On-ground analysis of the FXT data found a catalogued source within the ECLAIRs error circle at R.A., Dec. = 339.4966, 53.2393 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The position is consistent with EP260628c / EP J223759.5+531421 (Yang et al., ATel 17859; Coti Zelati et al. ATel 17909, Postigo et al., GCN 45272; Shi et al., GCN 45274; Wu et al., GCN 45275). The derived average unabsorbed flux is 3.65 (-0.10/+0.11) x 10^(-11) erg/s/cm^2 (0.5-10 keV; 1-sigma uncertainty). 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/45277. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43493] GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45270 SUBJECT: GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst DATE: 26/08/02 10:09:19 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Xin Feng (GXU), Hatsune Goto (RIKEN, CEA), Donghua Zhao (NAOC), Weinjin Xie (NAOC), Runchao CHEN (NJU), Feliu Lacreu (IAP), Diego Götz (CEA), report on behalf of the SVOM mission team: At 2026-08-02T09:23:10 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260802A (SVOM burst-id sb26080210). 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 Count-Rate Trigger (CRT), which produced a sequence of 3 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.09 in the [5-20] keV energy band starting at 2026-08-02T09:23:10. The localization of the best alert is R.A., Dec. 339.4431, 53.2195 degrees (J2000) with a 90% confidence level (C.L.) radius of 9.72 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs showed a single peak structure lasting about 0.2 seconds. We note that the magnetar EP J223759.5+531421(Atel #17859) is located in ECLAIRs error box, and given the short and soft nature of the burst, we suggest it is associated with this newly discovered magnetar. SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-08-02T09:25:42 UTC, 151 seconds after T0. Using onboard processed data we found a possible uncatalogued X-ray source with a low SNR, located at R.A., Dec. 339.439, 53.234 degrees: R.A. (J2000) = 22h37m45s Dec. (J2000) = 53d14m02s with a 90% C.L. radius of 161 arcseconds. This location is 0.89 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future 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 Wenjin Xie: xiewj(a)bao.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43492] GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45276 SUBJECT: GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit DATE: 26/08/02 16:50:27 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, C. Wu, Y. N. Ma, Y. L. Qiu, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), and J. T. Palmerio (CEA/Irfu), Wenjin Xie(NAOC), and Runchao Chen (NJU) report on behalf of the SVOM/VT team. VT performed observations with automatic slew of GRB 260802A triggered by SVOM/ECLAIRs (sb26080210, Feng et al., GCN 45270). The observation started at 2026-08-02T09:28:46.00 UTC, about 6.0 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. With X band data, no uncatalogued optical transient is detected in the stacked image at the position of the possible associate SGR EP J223759.5+531421 (Feng et al., GCN 45270; Postigo et al., GCN 45272; Shi et al., GCN 45274; Wu et al., GCN 45275). The following measurements are in AB magnitudes and are not corrected for Galactic extinction: Mid time (hr) | Exposure Time (s) | Band | Brightness (mag) 0.36 | 50*26 | VT_R | > 23.0 0.34 | 50*36 | VT_B | > 23.0 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/45276. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43491] GRB 260802A: SVOM/VT optical upper limits from VHF data
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45275 SUBJECT: GRB 260802A: SVOM/VT optical upper limits from VHF data DATE: 26/08/02 13:53:21 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu, L. P. Xin, Y.L. Qiu (NAOC), J. T. Palmerio (CEA/Irfu), Wenjin Xie (NAOC), Runchao CHEN (NJU) report on behalf of the SVOM/VT team. After the trigger by SVOM/ECLAIRs at 2026-08-02T09:23:10 UTC (T0), SVOM performed an automatic slew on the burst location (Feng et al., GCN 45270). SVOM/VT took images of the field in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via the VHF network, no uncatalogued optical source was detected within the MXT localization region (Feng et al., GCN 45270) in our three sequence images, compared to the Legacy Survey DR10. The suggested position of the magnetar EP J223759.5+531421 (Rea et al. ATel 17870; Coti Zelati et al. ATel 17909) falls within the subimage coverage. No optical counterpart was detected at this position. The 5-sigma upper limits are: | Mid time (min) | Band | Exposure (s) | 5-sigma upper limit (mag) | | :--- | :--- | :--- | :--- | | 6.43 | VT_B | 6 * 50 | > 21.5 | | 6.43 | VT_R | 6 * 50 | > 21.5 | | 100.32 | VT_R | 6 * 50 | > 21.5 | We note that the 1-bit subimage and source list do not fully cover the entire MXT uncertainty region. Radio or infrared follow-up observations are encouraged to further investigate the association with the magnetar candidate EP J223759.5+531421. 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/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/45275. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43490] GRB 260802A: LCO optical upper limits
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45274 SUBJECT: GRB 260802A: LCO optical upper limits DATE: 26/08/02 13:15:26 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y.Y. Shi (GXU), C. Wu, L.P. Xin (NAOC), A. Saccardi, D. Turpin (CEA/Irfu), R.C. Chen, W.J. Xie (BA-F), report on behalf of the SVOM mission team: We observed the field of GRB 260802A (SVOM burst-id sb26080210) detected by SVOM (Feng et al., GCN 45270) with the LCO 1m telescope at McDonald Observatory equipped with the Sinistro instrument. Our observation started on 2026-08-02 at 10:21:46 UT (about 58.6 min after the trigger) and we obtained 3x200 s exposures in the SDSS r filter. In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box. We measure the following upper limit calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction: r > 20.96 AB (5-sigma, mid-time 1.07 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/45274. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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