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GCN Circular 40558

Subject
Fermi trigger No 770058372: Global MASTER-Net observations report
Date
2025-05-28T04:02:49Z (11 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
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-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 GRB250527.71 (trigger No 770058372,02h 02m 09.60s , +15d 01m 48.0s, R=9.71) errorbox  35536 sec after notice time and 35573 sec after trigger time at 2025-05-28 02:59:01 UT, with upper limit up to  18.2 mag. The observations began at zenith distance = 78 deg. The sun  altitude  is -31.1 deg. 

The galactic latitude b = -44 deg., longitude l = 148 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2884026

We obtain a following upper limits.  

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

   35604 | 2025-05-28 02:59:01 |         MASTER-SAAO | (01h 24m 28.47s , +08d 41m 03.5s) |   C |    60 | 17.7 |        
   35767 | 2025-05-28 03:01:44 |         MASTER-SAAO | (01h 18m 04.52s , +12d 26m 58.9s) |   C |    60 | 17.8 |        
   36322 | 2025-05-28 03:10:59 |         MASTER-SAAO | (01h 24m 29.70s , +08d 40m 12.3s) |   C |    60 | 17.9 |        
   36402 | 2025-05-28 03:12:19 |         MASTER-SAAO | (01h 32m 29.52s , +08d 39m 17.3s) |   C |    60 | 18.1 |        
   36560 | 2025-05-28 03:14:57 |         MASTER-SAAO | (01h 18m 08.20s , +12d 28m 59.1s) |   C |    60 | 18.0 |        
   37115 | 2025-05-28 03:24:12 |         MASTER-SAAO | (01h 24m 28.68s , +08d 39m 13.6s) |   C |    60 | 18.0 |        
   37195 | 2025-05-28 03:25:31 |         MASTER-SAAO | (01h 32m 31.95s , +08d 41m 10.7s) |   C |    60 | 18.1 |        
   37354 | 2025-05-28 03:28:11 |         MASTER-SAAO | (01h 18m 12.02s , +12d 29m 02.7s) |   C |    60 | 18.0 |        
   37909 | 2025-05-28 03:37:26 |         MASTER-SAAO | (01h 24m 25.89s , +08d 39m 37.4s) |   C |    60 | 17.9 |        
   37988 | 2025-05-28 03:38:45 |         MASTER-SAAO | (01h 32m 34.75s , +08d 40m 49.6s) |   C |    60 | 18.2 |        
   38147 | 2025-05-28 03:41:24 |         MASTER-SAAO | (01h 18m 05.24s , +12d 29m 04.8s) |   C |    60 | 18.1 |        
   38544 | 2025-05-28 03:48:01 |         MASTER-SAAO | (01h 24m 25.46s , +08d 39m 20.1s) |   C |    60 | 18.0 |        
   38623 | 2025-05-28 03:49:20 |         MASTER-SAAO | (01h 32m 33.84s , +08d 41m 14.9s) |   C |    60 | 18.3 |        
   38782 | 2025-05-28 03:51:59 |         MASTER-SAAO | (01h 18m 04.65s , +12d 29m 03.5s) |   C |    60 | 18.1 |        
Filter C is a clear (unfiltred) band. 


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