GCN Circular 43073

Subject
Fermi GRB 251211B: Global MASTER-Net observations report
Event
GRB 251211B
Date
2025-12-12T00:15:55Z (a day 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-Tunka robotic telescope  [1]  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251211B ( Fermi GBM team, GCN 43072Loading...
 
 ) errorbox  622 sec after notice time and 629 sec after trigger time at 2025-12-11 20:42:33 UT, with upper limit up to  17.5 mag. The observations began at zenith distance = 72 deg. The sun  altitude  is -39.1 deg. 

The galactic latitude b = 48 deg., longitude l = 279 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3068576

We obtain a following upper limits.  

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

     643 | 2025-12-11 20:42:33 |        MASTER-Tunka | (11h 44m 16.21s , -11d 00m 25.5s) |   C |    25 | 16.9 |        
     665 | 2025-12-11 20:42:33 |        MASTER-Tunka | (11h 44m 16.21s , -11d 00m 25.6s) |   C |    70 | 17.5 |  Coadd 
     671 | 2025-12-11 20:43:02 |        MASTER-Tunka | (11h 44m 16.37s , -11d 00m 25.6s) |   C |    25 | 16.9 |        
     697 | 2025-12-11 20:43:30 |        MASTER-Tunka | (11h 44m 16.51s , -11d 00m 25.3s) |   C |    20 | 16.8 |        
Filter C is a clear (unfiltred) band. 


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

[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023,  Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.
http : // www.pereplet.ru/lipunov/625.html