TITLE: GCN CIRCULAR NUMBER: 17245 SUBJECT: GRB 141225A: MASTER-SAAO OT light curve DATE: 14/12/28 12:16:57 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs D.Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory E. Gorbovskoy,V. Lipunov, N.Tyurina, P.Balanutsa, D.Denisenko, M.Pruzhinskaya, A.Kuznetsov, V.Kornilov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute O.Gres, K.Ivanov, S.Yazev, N.M.Budnev, V.A.Poleshchuk Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinsky, I.Zalozhnih, A. Popov Ural Federal University, Kourovka H. Levato and C. Saffe Instituto de Ciencias Astronomicas de la Tierra y del Espacio (ICATE), San Juan, Argentina C. Mallamacci, C. Lopez and F. Podest Observatorio Astronomico Felix Aguilar (OAFA), San Juan National University, Argentina MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru) installed several days ago in South African Astronomical Observatory (Sutherland) was automatically pointed to the Swift and Fermi GRB 141225A (Avanzo et. al. GCN 17229). Firstly MASTER-SAAO pointed by FERMI coordinates and made first exposure 28 sec after FERMI trigger at 2014-12-25 23:02:28 UT (Buckley et al., 17233). Then MASTER-SAAO pointed to the Swift coordinates 20 sec after Swift notice time and 113 sec after trigger time at 2014-12-25 23:03:00 UT. The results of our photometery are: Start T-T_mid Exp. Mag Coadd UT s s unf ? 23:03:00 123 20 17.1 no 23:03:34 161 30 17.3 no 23:04:15 207 40 17.5 no 23:05:05 263 50 17.7 no 23:06:06 329 60 18.9 no 23:07:17 405 70 18.7 no 23:08:38 556 200 19.0 2 23:12:19 823 290 19.8 2 23:17:31 3161 3600 21.3 20 Our band is well described by a parity 0.8R+0.2B (USNO B1). The light curve from 113 to 300 power low index is about alpha ~= 0.76+-0.10 (F ~ t_-alpha) and alpha =~ 1.51 from 400 to 1500 . We see ~1 magnitude depression at 329 sec. The magnitudes in the table are not corrected for the Galactic extinction because its less than the our errors (Schlegel et al. 1998). The light curve is available at http://master.sai.msu.ru/static/GRB/GRB141225A.png This message may be cited.