TITLE: GCN CIRCULAR NUMBER: 41307 SUBJECT: Fermi GRB 250808A: Global MASTER-Net observations report DATE: 25/08/09 21:48:36 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs lipunov@xray.sai.msu.ru

V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)

MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250808A ( Fermi GBM team, GCN 41296) errorbox 18725 sec after notice time and 18749 sec after trigger time at 2025-08-08 23:37:41 UT, with upper limit up to 16.5 mag. The observations began at zenith distance = 79 deg. The sun altitude is -22.7 deg.

The galactic latitude b = -42 deg., longitude l = 211 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2964051

We obtain a following upper limits.

Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________

18779 | 2025-08-08 23:37:41 | MASTER-Kislovodsk | (03h 36m 57.03s , -13d 48m 11.9s) | C | 60 | 15.0 | 20676 | 2025-08-09 00:09:18 | MASTER-Kislovodsk | (03h 54m 25.00s , -15d 41m 27.8s) | C | 60 | 12.1 | 21637 | 2025-08-09 00:25:19 | MASTER-Kislovodsk | (04h 11m 41.65s , -22d 41m 02.9s) | C | 60 | 15.0 | 21697 | 2025-08-09 00:25:19 | MASTER-Kislovodsk | (04h 11m 41.66s , -22d 41m 03.0s) | C | 180 | 15.9 | Coadd 21720 | 2025-08-09 00:26:42 | MASTER-Kislovodsk | (04h 11m 34.93s , -22d 42m 01.6s) | C | 60 | 15.3 | 21806 | 2025-08-09 00:28:08 | MASTER-Kislovodsk | (04h 11m 43.16s , -22d 41m 36.9s) | C | 60 | 15.7 | 21889 | 2025-08-09 00:29:31 | MASTER-Kislovodsk | (04h 11m 39.40s , -22d 40m 19.5s) | C | 60 | 15.8 | 21949 | 2025-08-09 00:29:31 | MASTER-Kislovodsk | (04h 11m 39.42s , -22d 40m 19.8s) | C | 180 | 16.4 | Coadd 21979 | 2025-08-09 00:31:01 | MASTER-Kislovodsk | (04h 11m 39.61s , -22d 41m 49.4s) | C | 60 | 15.8 | 22063 | 2025-08-09 00:32:25 | MASTER-Kislovodsk | (04h 11m 43.91s , -22d 40m 21.3s) | C | 60 | 15.7 | 22151 | 2025-08-09 00:33:53 | MASTER-Kislovodsk | (04h 11m 36.12s , -22d 40m 49.1s) | C | 60 | 15.9 | 22211 | 2025-08-09 00:33:53 | MASTER-Kislovodsk | (04h 11m 36.14s , -22d 40m 49.5s) | C | 180 | 16.5 | Coadd 22232 | 2025-08-09 00:35:14 | MASTER-Kislovodsk | (04h 11m 37.37s , -22d 39m 46.9s) | C | 60 | 15.9 | 22315 | 2025-08-09 00:36:37 | MASTER-Kislovodsk | (04h 11m 43.55s , -22d 40m 44.4s) | C | 60 | 15.8 | 22398 | 2025-08-09 00:38:00 | MASTER-Kislovodsk | (04h 11m 38.67s , -22d 41m 40.3s) | C | 60 | 16.0 | 22482 | 2025-08-09 00:39:24 | MASTER-Kislovodsk | (04h 11m 43.85s , -22d 41m 24.6s) | C | 60 | 15.9 | 22752 | 2025-08-09 00:43:54 | MASTER-Kislovodsk | (04h 11m 43.50s , -22d 39m 33.3s) | C | 60 | 15.7 | 22834 | 2025-08-09 00:45:16 | MASTER-Kislovodsk | (04h 11m 39.63s , -22d 40m 21.8s) | C | 60 | 15.7 | 22894 | 2025-08-09 00:45:16 | MASTER-Kislovodsk | (04h 11m 39.63s , -22d 40m 21.9s) | C | 180 | 16.1 | Coadd 22919 | 2025-08-09 00:46:41 | MASTER-Kislovodsk | (04h 11m 37.85s , -22d 39m 18.0s) | C | 60 | 15.7 | 23011 | 2025-08-09 00:48:13 | MASTER-Kislovodsk | (04h 11m 44.98s , -22d 40m 14.4s) | C | 60 | 15.2 | 23093 | 2025-08-09 00:49:35 | MASTER-Kislovodsk | (04h 11m 39.09s , -22d 41m 10.2s) | C | 60 | 15.0 | 23153 | 2025-08-09 00:49:35 | MASTER-Kislovodsk | (04h 11m 39.09s , -22d 41m 10.2s) | C | 180 | 15.9 | Coadd 23199 | 2025-08-09 00:51:21 | MASTER-Kislovodsk | (04h 11m 44.24s , -22d 40m 39.2s) | C | 60 | 15.4 | 23283 | 2025-08-09 00:52:45 | MASTER-Kislovodsk | (04h 11m 42.44s , -22d 39m 17.6s) | C | 60 | 15.4 | 23381 | 2025-08-09 00:54:23 | MASTER-Kislovodsk | (04h 11m 42.54s , -22d 40m 34.8s) | C | 60 | 15.0 | 23467 | 2025-08-09 00:55:49 | MASTER-Kislovodsk | (04h 11m 45.72s , -22d 38m 58.4s) | C | 60 | 14.3 | 24214 | 2025-08-09 01:08:16 | MASTER-Kislovodsk | (04h 11m 48.73s , -22d 39m 27.6s) | C | 60 | 13.7 | 24300 | 2025-08-09 01:09:42 | MASTER-Kislovodsk | (03h 36m 57.33s , -13d 44m 50.9s) | C | 60 | 12.9 | Filter C is a clear (unfiltred) band.

The observation and reduction will continue. The message may be cited.

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