GCN Circular 24619

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.