TITLE: GCN CIRCULAR NUMBER: 15390 SUBJECT: GRB 131024B: MASTER prompt optical observation DATE: 13/10/27 11:38:44 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 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 GRB131024B 27 sec s after notice time and 36 sec after GRB time at 2013-10-24T21-36-07.864 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT error-box (Krimm et. al GCN15371). The 5-sigma upper limit has been about 17.2 mag. This is the prompt observations becaus GRB duration time T_90 = 64+-22 sec (Baumgartner et al., GCN Baumgartner). Such long circular delay was due to with daily power cut on observatory. The message may be cited.