TITLE: GCN CIRCULAR NUMBER: 24590 SUBJECT: LIGO/Virgo S190518bb Global MASTER-Net observations report DATE: 19/05/18 19:54:08 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the LIGO/Virgo S190518bb errorbox 443 sec after trigger time at 2019-05-18 19:26:44 UT, with upper limit up to 12.8 mag. The observations began at zenit distance = 129 deg. The sun altitude is -23.3 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=10403 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 488 | 2019-05-18 19:26:44 | MASTER-Kislovodsk | ( 21h 42m 42.23s , +32d 37m 35.79s) | C | 90 | 12.6 | 612 | 2019-05-18 19:28:38 | MASTER-Kislovodsk | ( 21h 42m 42.60s , +32d 37m 33.83s) | C | 110 | 12.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.