TITLE: GCN CIRCULAR NUMBER: 17558 SUBJECT: GRB 150309A: MASTER prompt optical observation DATE: 15/03/10 11:53:50 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, V.Kornilov, Lomonosov Moscow State University, Sternberg Astronomical Institute A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk V.Krushinsky, Ural Federal University, Yekaterinburg, 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 ( Lipunov et al., Advances in Astronomy, vol. 2010, pp. 1-7, MASTER Global Robotic Net, 2010) located in Kislovodsk was pointed to the GRB150309A 21 sec after notice time and 96 sec after trigger time at 2015-03-09 23:04:45 UT in two polarizations. On our first (20s exposure) set we not found optical transient within SWIFT error-box (Cummings et al GCN 17553) brighter then 17.2 Before this, the MASTER serial pointed to FERMI (trig. N 447634793) coordinates. Due to this pointings we have a two images from MASTER VWF very wide fild camera obtained at 2015-03-09 23:00:34 i.e. 152 sec before SWIFT BAT and 44 sec after FERMI GBM trigger times. We not found new OT on this 5 sec exposure images with upper limit 12.0 at SWIFT position. Table 1. GRB 150309A MASTER optical upper limits. Tstart Tst-T0 Tmid-T0 Expt Mlimit Instrum. Coadd. 23:00:34 -152 -149 5 12.0 MASTER VWF no 23:04:45 98 108 20 17.2 MASTER II no 23:04:45 98 559 780 19.3 MASTER II 10 23:20:20 1033 2363 2160 20.0 MASTER II 12 T0 - is a SWIFT trigger time. The message may be cited.