[vsnet-grb-info 27801] Fermi GRB 210427A: Global MASTER-Net observations report

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29904
SUBJECT: Fermi GRB 210427A: Global MASTER-Net observations report 
DATE:    21/04/27 05:45:22 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-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 210427A ( Fermi GBM team, GCN 29903) errorbox 83 sec after trigger time at 2021-04-27 04:58:36 UT, with upper limit up to  17.5 mag. The observations began at zenith distance = 41 deg. The sun  altitude  is -71.8 deg. 

The galactic latitude b =  8 deg., longitude l = 294 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1602343

We obtain a following upper limits.  

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

      93 | 2021-04-27 04:58:36 |         MASTER-OAFA | (11h 30m 41.80s , -52d 41m 19.0s) |   C |    20 | 16.8 |        
     149 | 2021-04-27 04:59:26 |         MASTER-OAFA | (11h 35m 39.45s , -51d 53m 30.7s) |   C |    30 | 17.0 |        
     203 | 2021-04-27 05:00:15 |         MASTER-OAFA | (11h 35m 46.94s , -51d 53m 27.2s) |   C |    40 | 17.1 |        
     267 | 2021-04-27 05:01:15 |         MASTER-OAFA | (11h 35m 42.92s , -51d 51m 45.2s) |   C |    50 | 17.2 |        
     342 | 2021-04-27 05:02:25 |         MASTER-OAFA | (11h 35m 42.91s , -51d 53m 27.9s) |   C |    60 | 17.3 |        
     432 | 2021-04-27 05:03:45 |         MASTER-OAFA | (11h 35m 45.38s , -51d 51m 52.5s) |   C |    80 | 17.4 |        
     542 | 2021-04-27 05:05:24 |         MASTER-OAFA | (11h 35m 40.74s , -51d 52m 31.1s) |   C |   100 | 17.5 |        
     671 | 2021-04-27 05:07:24 |         MASTER-OAFA | (11h 47m 58.15s , -52d 31m 41.5s) |   C |   120 | 17.3 |        
Filter C is a clear (unfiltred) band. 


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