TITLE: GCN CIRCULAR NUMBER: 13792 SUBJECT: GRB 120919B: MASTER prompt optical observations DATE: 12/09/21 13:54:00 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs 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) E. Gorbovskoy, V. Lipunov, V. Kornilov, D. Denisenko, A. Kuznetsov, D. Kuvshinov, A. Belinski, 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 MASTER-ICATE robotic Very Wide Field Cameras (FOV=2x384 square degrees, D=72mm, f/1.2, 1 pix = 22 arcsec, http://observ.pereplet.ru) located in Argentina (Observatorio Astronomico Felix Aguilar, http://93.180.27.230:8080/) were pointed to the GRB120919B by FERMI 369710066 trigger 30 s after notice time and 55 s after GRB time at 2012-09-19 01:15:18 UT. We cover full IPN-triangulations error-box (K. Hurley et. al. GCN13788) We haven`t found optical transient within IPN-triangulations error-box our first (5 s exposure) set and on coadd image with complete exposure of 45 seconds durnig gamma-burst activity (Golenetskii et al., GCN 13789). The 5-sigma upper limit on single image has been about 11.7 mag and 12.5 mag on coadded image. Also, we are marginaly see ~2 sigma OT at position Ra 20:10:26.40 Dec +37:31:48.00 with magnitude 12.5+-0.5m . The coverage map and OT image available here http://master.sai.msu.ru/static/GRB/GRB120919B_2x2deg.png Our cameras are continuously imaging the sky with 5 sec exposures. This message can be cited.