[vsnet-grb-info 27770] Fermi GRB 210421C: Global MASTER-Net observations report

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29873
SUBJECT: Fermi GRB 210421C: Global MASTER-Net observations report 
DATE:    21/04/21 21:30:14 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) started inspect of the Fermi GRB 210421C ( Fermi GBM team, GCN 29871) errorbox  3606 sec after notice time and 3636 sec after trigger time at 2021-04-21 21:13:29 UT, with upper limit up to  18.8 mag. The observations began at zenith distance = 24 deg. The sun  altitude  is -62.3 deg. 

The galactic latitude b =  1 deg., longitude l = 303 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1598370

We obtain a following upper limits.  

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

    3666 | 2021-04-21 21:13:29 |         MASTER-SAAO | (12h 44m 20.32s , -55d 59m 18.1s) |   C |    60 | 18.5 |        
    3839 | 2021-04-21 21:16:21 |         MASTER-SAAO | (13h 00m 06.56s , -55d 58m 20.2s) |   C |    60 | 17.6 |        
    3918 | 2021-04-21 21:17:41 |         MASTER-SAAO | (12h 35m 41.98s , -53d 57m 24.5s) |   C |    60 | 18.4 |        
    4248 | 2021-04-21 21:23:10 |         MASTER-SAAO | (12h 47m 33.26s , -53d 57m 52.4s) |   C |    60 | 18.8 |        
Filter C is a clear (unfiltred) band. 


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