TITLE:   GCN CIRCULAR
NUMBER:  31933
SUBJECT: Fermi  trigger No 672221879: Global MASTER-Net observations report 
DATE:    22/04/21 18:15:15 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, 
G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov,  D.Cheryasov, Ya.Kechin
(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
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez 
(INAOE, Guillermo Haro Astrophysics Observatory),

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

A. Gabovich, V.Yurkov 
(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 GRB220421.35 (trigger No 672221879,04h 57m 40.80s , +23d 08m 24.0s, R=2.09) errorbox  16459 sec after notice time and 32297 sec after trigger time at 2022-04-21 17:16:12 UT, with upper limit up to  15.4 mag. Observations started at twilight.  The observations began at zenith distance = 77 deg. The sun  altitude  is -14.4 deg. 

The galactic latitude b = -12 deg., longitude l = 179 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1950247

We obtain a following upper limits.  

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

   32328 | 2022-04-21 17:16:12 |         MASTER-SAAO | (04h 55m 32.93s , +23d 59m 04.1s) |   C |    60 | 15.1 |        
   32407 | 2022-04-21 17:17:31 |         MASTER-SAAO | (05h 04m 15.50s , +24d 00m 52.6s) |   C |    60 | 15.4 |        
   33239 | 2022-04-21 17:31:23 |         MASTER-SAAO | (05h 09m 08.86s , +25d 54m 24.7s) |   C |    60 | 15.2 |        
   33413 | 2022-04-21 17:34:17 |         MASTER-SAAO | (05h 04m 26.29s , +24d 01m 23.3s) |   C |    60 | 14.1 |        
   33492 | 2022-04-21 17:35:36 |         MASTER-SAAO | (05h 00m 15.90s , +22d 07m 05.2s) |   C |    60 | 13.8 |        
Filter C is a clear (unfiltred) band. 


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