TITLE: GCN CIRCULAR NUMBER: 17689 SUBJECT: GRB 150413A: MASTER bright OT detection DATE: 15/04/13 14:21:11 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University 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 A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov 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) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka was pointed to the GRB150413A (Markwardt et al. GCN 17688) 132 sec after trigger time at 2015-04-13 13:57:10 UT in two polarizations. We see bright OT at: RA, Dec = 12 41 41.98 +71 50 28.0 Mag = 16.1 (unfiltered 0.2B +0.8R UsnoB1) The discovery image is available at https://master.sai.msu.ru/static/OT/grb150413A.jpg The message may be cited.