TITLE: GCN CIRCULAR NUMBER: 27917 SUBJECT: Swift GRB200612.19: Global MASTER-Net OT detection DATE: 20/06/12 05:17:43 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, A.V. Krylov, I. Gorbunov, D. Vlasenko, F. Balakin Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk K. Ivanov, O. Gres, N.M. Budnev, S.Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the GRB200612.19 19 sec after notice time and 495 sec after trigger time at 2020-06-12 04:47:52 UT. On our 4-th (180s exposure) set , obtained 960 sec after tigger time at 2020-06-12 04:55:38 UT, we found 1 optical transient within Swift error-box (ra=302.679 dec=-45.3569 r=0.05) brighter than 18.2. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 1050 2020-06-12 04:55:38 180 (20h 10m 48.64s , -45d 20m 06.7s) 17.9 The 5-sigma upper limit has been about 18.2mag The message may be cited.