TITLE: GCN CIRCULAR NUMBER: 41271 SUBJECT: Swift GRB250807.65: Global MASTER-Net observations report DATE: 25/08/07 18:44:25 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB250807.65 (trigger No 1340561,01h 02m 20.40s , -59d 05m 38.4s, R=0.05) errorbox 10317 sec after notice time and 10401 sec after trigger time at 2025-08-07 18:36:29 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 76 deg. The sun altitude is -32.1 deg.

The galactic latitude b = -58 deg., longitude l = 300 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2963168

We obtain a following upper limits.

Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________

10491 | MASTER-SAAO | C | 180 | 17.1 | 10491 | MASTER-SAAO | C | 180 | 17.8 | Filter C is a clear (unfiltred) band.

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

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