TITLE:   GCN CIRCULAR
NUMBER:  30132
SUBJECT: Fermi GRB 210606A: Global MASTER-Net observations report 
DATE:    21/06/06 05:02:24 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-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210606A ( Fermi GBM team, GCN 30131) errorbox  707 sec after notice time and 735 sec after trigger time at 2021-06-06 04:08:17 UT, with upper limit up to  17.4 mag. The observations began at zenith distance = 74 deg. The sun  altitude  is -79.9 deg. 

The galactic latitude b = 59 deg., longitude l = 274 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1629491

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     765 | 2021-06-06 04:08:17 |         MASTER-OAFA | (11h 48m 10.39s , +00d 06m 01.9s) |   C |    60 | 16.3 |        
    1046 | 2021-06-06 04:12:58 |         MASTER-OAFA | (11h 56m 10.96s , +00d 05m 07.4s) |   C |    60 | 17.1 |        
    1206 | 2021-06-06 04:15:38 |         MASTER-OAFA | (11h 56m 17.42s , +02d 00m 54.3s) |   C |    60 | 15.7 |        
    1286 | 2021-06-06 04:16:57 |         MASTER-OAFA | (11h 48m 44.03s , -01d 47m 01.2s) |   C |    60 | 17.0 |        
    1365 | 2021-06-06 04:18:17 |         MASTER-OAFA | (11h 56m 52.70s , -01d 47m 56.7s) |   C |    60 | 17.4 |        
Filter C is a clear (unfiltred) band. 


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