TITLE: GCN CIRCULAR NUMBER: 21040 SUBJECT: GRB170426.95 MASTER-Net OT detection DATE: 17/04/27 00:54:16 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Kislovodsk was pointed to the GRB170426.95 894 sec after notice time and 982 sec after trigger time at 2017-04-26 23:00:43 UT. On our 6-th (180s exposure) set we found 1 optical transient within SWIFT error-box (ra=184.879 dec=5.65583 r=0.066667) brighter then 18.91. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 1072 2017-04-26 23:00:43 180 (12h 19m 39.17s , +05d 37m 42.5s) 16.08 The 5-sigma upper limit has been about 18.91mag The message may be cited.