TITLE: GCN CIRCULAR NUMBER: 15176 SUBJECT: GRB 130903A: MASTER early optical limit DATE: 13/09/04 10:07:29 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, D. Denisenko, V. Kornilov, A. Kuznetsov, D. Kuvshinov, N. Tyurina, N. Shatskiy, P. Balanutsa, D. Zimnukhov, V.V. Chazov Lomonosov Moscow 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 H. Levato and C. Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) C. Mallamaci, C. Lopez and F. Podest Observatorio Astronomico Felix Aguilar (OAFA) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Kislovodsk was pointed to the GRB130903A 240 sec after notice time and 244 sec after GRB time at 2013-09-03 00:51:36 UT in two polarizations. Some delay was due to weather condition. On our first (40s exposure) set we haven`t found optical transient within INTEGRAL error-box (S.Mereghetti et. al. GCN-15169 ). The 5-sigma upper limit has been about 15.0 mag in each of polarization. On best coadd image (with use of the first 12 sets on 6 in each of polyarization) with total exposition 900 sec and middle time 504 after GRB time upper limit is 17.5 mag. More detailed information in the following table: T_start T_finish T_mid t_mid-t_trig Exptime Filter Limit Coadd --------------------------------------------------------------------------- 00:51:36 00:52:16 00:51:36 264 s 40 s P| 15.0 no 00:51:36 00:52:16 00:51:36 264 s 40 s P- 15.0 no 00:51:36 00:52:16 00:51:36 264 s 80 s P| + P- 15.5 2 00:51:36 01:00:16 00:55:56 504 s 450 s P| 17.0 6 00:51:36 01:00:16 00:55:56 504 s 450 s P- 17.0 6 00:51:36 01:00:16 00:55:56 504 s 900 s P| + P- 17.5 12 P- and P| is a RA and DEC orientated polaroids. The message may be cited.