TITLE: GCN CIRCULAR NUMBER: 13309 SUBJECT: GRB 120521B/Fermi Trigger 359284074: early MASTER-ICATE optical limit DATE: 12/05/21 10:49:58 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs 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) E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, D.Denisenko, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, A.Kuznetsov Moscow Lomonosov State University, Sternberg Astronomical Institute, A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk V.Krushinski, I.Zalozhnich, A. Popov, A. Bourdanov, A. Punanova Ural Federal University MASTER VWF robotic cameras (400 square degrees, 1 pix = 22 arcsec, http://observ.pereplet.ru) located in Argentina (Observatorio Astronomico Felix Aguilar) was pointed to the Fermi Trigger 359284074 12 sec before Swift notice time and 65 sec after Swift trigger (Cummings et al., GCN Circ 13305) time at 2012-05-21 09:08:53 UT. On our first image (5 sec exposure) we have not found any OT. T_start(UT) T - T_trig MeanTime Exp Limit Coadd? Filter ---------------------------------------------------------------------- 09 08 53 65 s 67.5s 5s 11.5 No Unfiltered 09 08 53 65 s 77.5s 25s 12.4 Yes Unfiltered The message may be cited.