TITLE: GCN CIRCULAR NUMBER: 41232 SUBJECT: Swift GRB250805.26: Global MASTER-Net observations report DATE: 25/08/05 06:16:56 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB250805.26 (trigger No 1339848,01h 36m 36.72s , -81d 24m 21.6s, R=0.05) errorbox 18 sec after notice time and 44 sec after trigger time at 2025-08-05 06:09:52 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 53 deg. The sun altitude is -65.4 deg.

The galactic latitude b = -36 deg., longitude l = 301 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2960226

We obtain a following upper limits.

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

49 | MASTER-OAFA | C | 10 | 17.6 | 65 | MASTER-OAFA | C | 10 | 17.6 | 87 | MASTER-OAFA | C | 20 | 17.9 | 113 | MASTER-OAFA | C | 20 | 17.9 | Filter C is a clear (unfiltred) band.

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

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