GCN Circular 42728

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-Tavrida robotic telescope  [1]  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the LAT GRB251117.51 (trigger No 785074797,22h 05m 12.00s , +05d 34m 12.0s, R=0.719833) errorbox 11108 sec after trigger time at 2025-11-17 15:25:00 UT, with upper limit up to  16.0 mag. Observations started at twilight.  The observations began at zenith distance = 39 deg. The sun  altitude  is -12.7 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the LAT GRB251117.51 errorbox 12105 sec after trigger time at 2025-11-17 15:41:37 UT, with upper limit up to  17.0 mag. The observations began at zenith distance = 38 deg. The sun  altitude  is -21.1 deg. 

The galactic latitude b = -39 deg., longitude l = 67 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3044995

We obtain a following upper limits.  

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

   11138 | 2025-11-17 15:25:00 |      MASTER-Tavrida | (22h 06m 43.82s , +05d 59m 20.3s) |   C |    60 | 15.1 |        
   11222 | 2025-11-17 15:26:23 |      MASTER-Tavrida | (22h 10m 15.32s , +07d 18m 57.3s) |   C |    60 | 16.0 |        
   11379 | 2025-11-17 15:29:01 |      MASTER-Tavrida | (22h 03m 42.52s , +04d 40m 48.3s) |   C |    60 | 16.0 |        
   12135 | 2025-11-17 15:41:37 |   MASTER-Kislovodsk | (22h 06m 52.64s , +05d 11m 31.5s) |   C |    60 | 16.6 |        
   12215 | 2025-11-17 15:42:57 |   MASTER-Kislovodsk | (22h 03m 51.57s , +03d 16m 19.2s) |   C |    60 | 16.4 |        
   12299 | 2025-11-17 15:44:20 |      MASTER-Tavrida | (22h 01m 29.12s , +03d 23m 18.8s) |   C |    60 | 16.0 |        
   13003 | 2025-11-17 15:56:04 |      MASTER-Tavrida | (21h 59m 50.40s , +07d 17m 56.1s) |   C |    60 | 15.8 |        
   13672 | 2025-11-17 16:07:13 |      MASTER-Tavrida | (21h 55m 17.37s , +05d 59m 54.8s) |   C |    60 | 16.0 |        
   13882 | 2025-11-17 16:10:44 |   MASTER-Kislovodsk | (21h 56m 10.36s , +07d 02m 54.9s) |   C |    60 | 17.0 |        
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