TITLE: GCN CIRCULAR NUMBER: 23850 SUBJECT: GRB 190203A: MASTER OT detection DATE: 19/02/03 23:55:04 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, A. Chasovnikov, D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational State University), A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), O. Gress, N.M. Budnev, O.Ershova, Yu.Ishmuhametova (Applied Physics Institute, Irkutsk State University), R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE) MASTER-Amur robotic telescope (Global MASTER-Net http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, v.2010, 30L) was pointed to Swift GRB190203B (Lien et al. GCN23845, Ttrig=2019-02-03 15:44:08 UT) 19 sec after notice time (63 sec after trigger time) at 2019-02-03 15:45:11 UT. On our first (10s exposure) set we found 1 optical transient within SWIFT error-box: T-Tmid Date Time Exp,s Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 68 2019-02-03 15:45:11 10 (01h 30m 23.25s , +55d 43m 20.59s) 15.28 There is fast decay on the light curve. The 5-sigma upper limit on the first 10s exposition was 16.3mag The galactic latitude b = -6 deg., longitude l = 129 deg. The observations started on zenit distance = 61 deg. The sun altitude was -56.2 deg The message may be cited.