TITLE:   GCN CIRCULAR
NUMBER:  40525
SUBJECT: Fermi  trigger No 769499303: Global MASTER-Net observations report
DATE:    25/05/22 10:47:55 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, 
G.Antipov,  A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

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 GRB250521.24 (trigger No 769499303,12h 46m 07.20s , -30d 31m 48.0s, R=12.01) errorbox  60162 sec after notice time and 60196 sec after trigger time at 2025-05-21 22:31:35 UT, with upper limit up to  19.0 mag. Observations started at twilight.  The observations began at zenith distance = 39 deg. The sun  altitude  is -10.4 deg. 

The galactic latitude b = 32 deg., longitude l = 302 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2877064

We obtain a following upper limits.  

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

   60216 | 2025-05-21 22:31:35 |         MASTER-OAFA | (13h 05m 11.76s , -37d 11m 03.5s) |   C |    40 | 16.7 |        
   60227 | 2025-05-21 22:31:35 |         MASTER-OAFA | (13h 16m 35.65s , -36d 46m 35.5s) |   C |    60 | 12.6 |        
   60386 | 2025-05-21 22:34:25 |         MASTER-OAFA | (13h 05m 09.04s , -35d 17m 27.8s) |   C |    40 | 17.0 |        
   60397 | 2025-05-21 22:34:25 |         MASTER-OAFA | (13h 16m 15.99s , -34d 53m 05.7s) |   C |    60 | 18.7 |        
   60555 | 2025-05-21 22:37:14 |         MASTER-OAFA | (12h 52m 33.75s , -29d 34m 03.7s) |   C |    40 | 17.4 |        
   60566 | 2025-05-21 22:37:14 |         MASTER-OAFA | (13h 03m 00.21s , -29d 09m 57.2s) |   C |    60 | 19.0 |        
Filter C is a clear (unfiltred) band. 


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