TITLE:   GCN CIRCULAR
NUMBER:  29627
SUBJECT: Swift GRB 210308A: Global MASTER-Net observations report 
DATE:    21/03/08 22:18:11 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@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 GRB 210308A ( V. D'Elia et al., GCN 29619) errorbox  40899 sec after notice time and 40918 sec after trigger time at 2021-03-08 17:59:54 UT, with upper limit up to  13.9 mag. Observations started at twilight.  The observations began at zenith distance = 74 deg. The sun  altitude  is -12.2 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210308A errorbox  55958 sec after notice time and 55976 sec after trigger time at 2021-03-08 22:10:53 UT, with upper limit up to  18.5 mag. The observations began at zenith distance = 48 deg. The sun  altitude  is -40.8 deg. 

The galactic latitude b = -7 deg., longitude l = 164 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1563625

We obtain a following upper limits.  

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

   21950 |             MASTER- |   C |    60 | 18.0 |        
   22210 |             MASTER- |   C |    60 | 15.8 |        
   22945 |             MASTER- |   C |    60 | 12.6 |        
   41008 |         MASTER-SAAO |   C |   180 | 13.9 |        
   56067 |          MASTER-IAC |   C |   180 | 18.5 |        
Filter C is a clear (unfiltred) band. 


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