[vsnet-grb-info 28192] Swift GRB210621.71: Global MASTER-Net observations report

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30295
SUBJECT: Swift GRB210621.71: Global MASTER-Net observations report 
DATE:    21/06/21 17:17:26 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

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




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 Swift GRB210621.71 (trigger No 1057131,15h 55m 14.88s , -54d 03m 46.8s, R=0.05) errorbox 79 sec after trigger time at 2021-06-21 17:05:55 UT, with upper limit up to  16.6 mag. The observations began at zenith distance = 43 deg. The sun  altitude  is -17.3 deg. 

The galactic latitude b = -1 deg., longitude l = 328 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1641828

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      89 |         MASTER-SAAO | P\  |    20 | 15.6 |        
     129 |         MASTER-SAAO | P\  |    20 | 16.0 |        
     173 |         MASTER-SAAO | P\  |    30 | 16.1 |        
     228 |         MASTER-SAAO | P\  |    40 | 15.6 |        
     292 |         MASTER-SAAO | P\  |    50 | 16.6 |        
     372 |         MASTER-SAAO | P\  |    70 | 16.6 |        


The observation and reduction will continue. 
The message may be cited.