TITLE: GCN CIRCULAR NUMBER: 30352 SUBJECT: Swift GRB210702.80: Global MASTER-Net OT detection DATE: 21/07/02 19:32:56 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, F. Balakin, I. Gorbunov Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University 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 R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the GRB210702.80 17 sec after notice time and 822 sec after trigger time at 2021-07-02 19:20:56 UT. On our first (160s exposure) set we found 1 optical transient within Swift error-box (ra=168.567 dec=-36.7408 r=0.05) brighter than 18.1. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 902 2021-07-02 19:20:56 160 (11h 14m 18.85s , -36d 44m 49.1s) 12.3 The 5-sigma upper limit has been about 18.1mag The message may be cited.