TITLE: GCN CIRCULAR NUMBER: 18697 SUBJECT: GRB 151215A: MASTER early OT detection and light curve DATE: 15/12/15 12:19:35 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs R. Rebolo, M. Serra-Ricart, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias E. Gorbovskoy, V. Lipunov, N.Tyurina, D. Vlasenko, V.Kornilov, P.Balanutsa, A.Kuznetsov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institute O. Gress, K. Ivanov, N.M. Budnev, V.A. Poleshchuk, S.A. Yazev Irkutsk State University V.Yurkov, Yu.Sergienko, A.Gabovich, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk report on behalf of the MASTER Team: MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 34917111) located in IAC was pointed to the GRB151215A (Gibson et al. GCN 18691) 18 sec after notice time and 33 sec after trigger time at 2015-12-15 03:02:05 UT with 10s exposition in two perpendicular polarization planes. We detect OT (Cenko et al GCN 18691, Wiseman et al. GCN 18694) in first image with magnitude 17.8 +- 0.5 at a growing stage (midle time 38 sec after trigger). We definetely see OT on all images till 1500-th second. The GRB optical light curve have a maximum at third image (110 s after triger time) with 17.0 +- 0.1 mag. The automatic light curve in one polarization available here http://master.sai.msu.ru/static/GRB151215A_v1.png All magnitudes are unfiltered (0.2B+0.8R) with respect to number USNO B1.0 stars. This is preliminary results. The message may be cited.