TITLE: GCN CIRCULAR NUMBER: 24619 SUBJECT: LIGO/Virgo S190521g Global MASTER-Net observations report DATE: 19/05/21 04:01:24 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko (Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University) A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk (Irkutsk State University) V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University, Blagoveschensk) R. Podesta, Carlos Lopez and F. Podesta (Observatorio Astronomico Felix Aguilar (OAFA)) Hugo Levato and Carlos Saffe (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias) D. Buckley, S. Potter, A. Kniazev, M. Kotze (South African Astronomical Observatory) 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) started inspect of the LIGO/Virgo S190521g errorbox 429 sec after trigger time at 2019-05-21 03:09:38 UT, with upper limit up to 19.4 mag. The observations began at zenit distance = 60 deg. The sun altitude is -28.2 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the LIGO/Virgo S190521g errorbox 578 sec after trigger time at 2019-05-21 03:12:07 UT, with upper limit up to 16.4 mag. The observations began at zenit distance = 133 deg. The sun altitude is -69.1 deg. The galactic latitude b = -60 deg., longitude l = 98 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/ligo_1.php?id=10405 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 474 | 2019-05-21 03:09:38 | MASTER-SAAO | ( 0h 29m 35.15s , -66d 12m 40.55s) | C | 90 | 18.4 | 599 | 2019-05-21 03:09:38 | MASTER-SAAO | ( 0h 29m 35.15s , -66d 12m 40.54s) | C | 340 | 19.4 | Coadd 604 | 2019-05-21 03:11:37 | MASTER-SAAO | ( 0h 29m 56.68s , -66d 12m 35.01s) | C | 110 | 18.6 | 639 | 2019-05-21 03:12:07 | MASTER-OAFA | ( 0h 18m 54.28s , -66d 16m 16.13s) | C | 120 | 16.3 | 757 | 2019-05-21 03:13:55 | MASTER-SAAO | ( 0h 29m 57.51s , -66d 12m 34.78s) | C | 140 | 18.6 | 1057 | 2019-05-21 03:18:35 | MASTER-OAFA | ( 0h 18m 54.17s , -66d 16m 16.79s) | C | 180 | 16.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.