TITLE: GCN CIRCULAR NUMBER: 19425 SUBJECT: GRB 160509A MASTER-NET observations DATE: 16/05/12 10:27:08 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, 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) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Blagoveschensk was pointed to the GRB160509A (Longo et al GCN 19403) 15306 sec after trigger time at 2016-05-09 13:14:10 UT directly after sunset. On our first (180s exposure) set we not found optical transient brighter then 18.5m on single (180 s) and 20.0m on coadd (total exposure 1800 s) images at x-ray (Kennea et al GCN 19408) and optical (Levan et al 19410, Alexander et al GCN 19414, Cenko et al GCN 19416, Schmidl et al GCN 19421) position. The message may be cited.