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GCN Circular 40770

Subject
Fermi trigger No 771886893: Global MASTER-Net observations report
Date
2025-06-18T06:45:32Z (2 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-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 GRB250617.88 (trigger No 771886893,21h 51m 52.80s , +32d 45m 00.0s, R=6.71) errorbox  30646 sec after notice time and 30797 sec after trigger time at 2025-06-18 05:34:46 UT, with upper limit up to  18.7 mag. The observations began at zenith distance = 80 deg. The sun  altitude  is -74.8 deg. 

The galactic latitude b = -17 deg., longitude l = 85 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2906384

We obtain a following upper limits.  

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

   30888 | 2025-06-18 05:34:46 |         MASTER-OAFA | (22h 13m 06.89s , +32d 25m 32.4s) |   C |   180 | 17.3 |        
   31437 | 2025-06-18 05:44:55 |         MASTER-OAFA | (22h 11m 56.61s , +32d 28m 43.0s) |   C |    60 | 17.4 |        
   31517 | 2025-06-18 05:46:15 |         MASTER-OAFA | (22h 11m 55.21s , +32d 30m 09.7s) |   C |    60 | 17.7 |        
   32153 | 2025-06-18 05:55:51 |         MASTER-OAFA | (22h 13m 12.62s , +32d 28m 14.3s) |   C |   180 | 18.2 |        
   32789 | 2025-06-18 06:07:27 |         MASTER-OAFA | (22h 11m 57.63s , +32d 30m 11.6s) |   C |    60 | 18.1 |        
   32867 | 2025-06-18 06:08:45 |         MASTER-OAFA | (22h 11m 56.00s , +32d 29m 13.9s) |   C |    60 | 18.1 |        
   33439 | 2025-06-18 06:17:17 |         MASTER-OAFA | (22h 13m 03.73s , +32d 26m 36.5s) |   C |   180 | 18.6 |        
   34302 | 2025-06-18 06:32:40 |         MASTER-OAFA | (22h 11m 52.28s , +32d 30m 23.0s) |   C |    60 | 18.7 |        
Filter C is a clear (unfiltred) band. 


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