[vsnet-grb-info 28156] Swift GRB210619.99: Global MASTER-Net OT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30259
SUBJECT: Swift GRB210619.99: Global MASTER-Net OT detection
DATE:    21/06/20 00:05:14 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa,
A.Kuznetsov, D. Vlasenko, F. Balakin, I. Gorbunov
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

D. Buckley, S. Potter, A. Kniazev, M. Kotze
South African Astronomical Observatory

K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk
Irkutsk State University

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

V. Yurkov, A. Gabovich, Yu. Sergienko
Blagoveschensk Educational State University, Blagoveschensk

R. Podesta, Carlos Lopez and F. Podesta
Observatorio Astronomico Felix Aguilar (OAFA)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

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) was pointed to the  GRB210619.99 22 sec after notice time and 36 sec after trigger time at 2021-06-20 00:00:02 UT. On our first (10s exposure)  set we  found 1 optical transient within Swift error-box (ra=319.708 dec=33.86 r=0.05) brighter than  15.3.


 T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
      41   2021-06-20 00:00:02      10   (21h 18m 52.35s , +33d 51m 01.4s)     10.4

The 5-sigma upper limit has been about  15.3mag
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