TITLE: GCN CIRCULAR NUMBER: 41308 SUBJECT: EP250807a: Global MASTER-Net observations report DATE: 25/08/09 21:49:54 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) was pointed to the EP250807a ( EP Team et al., GCN 41277) errorbox 36084 sec after notice time and 64631 sec after trigger time at 2025-08-08 17:30:13 UT, with upper limit up to 17.1 mag. Observations started at twilight. The observations began at zenith distance = 33 deg. The sun altitude is -11.5 deg.

The galactic latitude b = 7 deg., longitude l = 45 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2963680

We obtain a following upper limits.

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

64661 | 2025-08-08 17:30:13 | MASTER-Kislovodsk | (18h 43m 28.97s , +14d 43m 36.5s) | C | 60 | 17.1 | 64831 | 2025-08-08 17:33:02 | MASTER-Kislovodsk | (18h 43m 28.20s , +14d 42m 55.0s) | C | 60 | 17.1 | 65007 | 2025-08-08 17:35:59 | MASTER-Kislovodsk | (18h 43m 24.84s , +14d 43m 09.9s) | C | 60 | 17.1 | Filter C is a clear (unfiltred) band.

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

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