TITLE: GCN CIRCULAR NUMBER: 19821 SUBJECT: GRB 160816A: MASTER OT early detection on coaded images DATE: 16/08/18 16:25:19 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs N.Tyurina, E. Gorbovskoy, V. Lipunov, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov Lomonosov Moscow State University, Sternberg Astronomical Institute R. Rebolo, M. Serra, N. Lodieu, G. Israelian The Instituto de Astrofisica de Canarias K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, Irkutsk State University D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory A. Tlatov, V.Senik, D. Dormidontov, A.Parkhomenko Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk Hugo Levato, Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R.Podesta, C.Mallamaci, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in IAC was pointed to the GRB160816.73 24 sec after notice time and 18726 sec after trigger time at 2016-08-16 22:43:04 UT. (We corrected start exposition time which published in previouse MASTER circular (Lipunov et al., GCN 19805). We reducted coadded images and found OT. We see OT on coadded images inside SWIFT XRT (Kennea et al., GCN19806) at LCOGT position (Guidorzi et al., GCN 19808, Kuin et al., GCN 19815) on two tubes with unfiltered magnitude calibrated by USNO B1 stars ( m = 0.2B+0.8R ): m_OT=20.5 (+0.5 -0.2) at mean exposition time 2016-08-16 23:05:53, 20095 sec (5.58 hours) after GBM trigger time. T_start =18762sec, T_end=21464 after trigger. The total exposition = 1800 sec. The images is available at http://observ.pereplet.ru/images/GRB160816AMASTER.jpg The message may be cited.