TITLE: GCN CIRCULAR NUMBER: 20102 SUBJECT: GRB 161023A (Integral trigger 7613) MASTER-Net bright OT detection DATE: 16/10/23 23:06:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A. Gabovich Blagoveschensk Educational State University, Blagoveschensk V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the GRB161023.94 24 sec after notice time and 33 sec after trigger time at 2016-10-23 22:39:24 UT in two polarization. On our first (10s exposure) and consequent images we found optical bright transient within INTEGRAL error-box (ra=20 45 08 dec=-47 37 08 r=0.054667) at following position: RA Dec 20h 44m 05.21s , -47d 39m 48s.5 OT rise up to maximum magnituge about 12.5 (~ 3 minutes after the trigger). The 5-sigma upper limit at first has been about 16.11mag The message may be cited.