TITLE: GCN CIRCULAR NUMBER: 24693 SUBJECT: GRB 190530A: optical afterglow detection by 5 MASTER telescopes DATE: 19/05/31 09:46:11 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov (Lomonosov MSU), D.Svinkin (Ioffe Institute), J.Greiner (MPG, Germany), D.Vlasenko, O.Gress, I.Gorbunov, E.Gorbovskoy, A.Kuznetsov, V.Kornilov, V.Vladimirov, P.Balanutsa, D.Zimnukhov, F.Balakin, N.Tiurina, A. Chasovnikov, V.Topolev, V.Senik, D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department), V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational State University), O. Gress, N.M. Budnev, O.Ershova, S.Yazev (Applied Physics Institute, Irkutsk State University), A. Tlatov, D.Dormidontov, A.V. Parhomenko (Kislovodsk Solar Station of the Pulkovo Observatory), R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA, San Juan National University), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE, SJNU) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), MASTER Global Robotic Net (Lipunov et al., 2010, Advances in Astronomy,vol.2010, 30L (http://observ.pereplet.ru) observed Fermi GRB 190530A (GBM team GCN 24676, BALROG Biltzinger et al.GCN 24677, LAT Longo et al. GCN 24679 and IPN localization; gamma-ray transient also detected by AGILE 8s later Lecarelli et al. GCN 24678, Verrecchia et al. GCN 24683) in MASTER-Amur, MASTER-Tunka, MASTER-SAAO, MASTER-Kislovodsk, MASTER-Tavrida, MASTER-IAC (the order in accordance with sunset). MASTER auto-detection system discovered MASTER OT J080207.73+352847.7 = AT 2019gdw (https://wis-tns.weizmann.ac.il/object/2019gdw ) at (RA,Dec2000)=08h 02m 07.73s +35d 28m 47.7s( Lipunov et al. GCN24680) MASTER-Amur robotic telescope automatically was pointed to the Fermi GRB190530A BALROG localization at 2019-05-30 14:34:09 (error-box altitude = 13 (and go down), sun_alt=-17 very cloudy weather at sunset) with automatic photometry m_OT ~ 14.8 MASTER-Tunka robotic telescope automatically was pointed to the GRB190530A at 2019-05-30 14:43:13UT (error_box_alt=26deg., sun_alt=-10deg.), automatic photometry m_OT ~ 16.5 MASTER-SAAO robotic telescope automatically was pointed to the GRB190530A at 2019-05-30 16:34:41UT (very cloudy all horizont, error-box_alt=13.5 and go down, sun_alt=-11) mlim=14.5 MASTER-Kislovodsk robotic telescope automatically was pointed to the GRB190530A at 2019-05-30 18:12:10 (sun altitute= -16deg., alert_altitute=23deg.) automatic photometry m_OT~16.7 MASTER-Tavrida robotic telescope automatically was pointed to the GRB190530A at 2019-05-30 2019-05-30 18:12:17 (sun altitute= -8deg., alert_altitute=34deg.) automatic photometry m_OT~16.7 MASTER-IAC robotic telescope automatically was pointed to the GRB190530A at 2019-05-30 20:50:32UT (sun altitute=-11 deg., alert_altitute=36 deg.) automatic photometry unfiltered m_OT~17.4 The covered map and OT place is available at https://master.sai.msu.ru/site/master2/event.php?id=1034468 Observation and reduction will be continued. The message may be cited.