TITLE: GCN CIRCULAR NUMBER: 40735 SUBJECT: Swift GRB250615.93: Global MASTER-Net observations report DATE: 25/06/15 22:32:26 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 GRB250615.93 (trigger No 1324646,19h 21m 22.56s , +04d 40m 19.2s, R=0.05) errorbox 25 sec after notice time and 42 sec after trigger time at 2025-06-15 22:26:02 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 46 deg. The sun altitude is -80.9 deg.

The galactic latitude b = -5 deg., longitude l = 41 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2903527

We obtain a following upper limits.

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

48 | MASTER-SAAO | C | 10 | 16.9 | 48 | MASTER-SAAO | C | 10 | 17.1 | 77 | MASTER-SAAO | C | 10 | 17.0 | 77 | MASTER-SAAO | C | 10 | 17.1 | Filter C is a clear (unfiltred) band.

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

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