GCN Circular 43240

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) was pointed to the IceCube Alert 251225.84 (trigger No 19814286,19h 49m 58.80s , +22d 27m 50.4s, R=0.51) errorbox  12800 sec after notice time and 12867 sec after trigger time at 2025-12-25 23:48:34 UT, with upper limit up to  15.5 mag. Observations started at twilight.  The observations began at zenith distance = 80 deg. The sun  altitude  is -11.8 deg. 

The galactic latitude b = -2 deg., longitude l = 60 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3085150

We obtain a following upper limits.  

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

   12873 | 2025-12-25 23:48:34 |        MASTER-Tunka | (19h 49m 23.32s , +22d 04m 38.1s) |   C |    10 | 15.4 |        
   12873 | 2025-12-25 23:48:34 |        MASTER-Tunka | (19h 49m 40.90s , +21d 58m 08.5s) |   C |    10 | 14.5 |        
   12896 | 2025-12-25 23:48:57 |        MASTER-Tunka | (19h 49m 29.45s , +22d 03m 37.1s) |   C |    10 | 15.3 |        
   12896 | 2025-12-25 23:48:57 |        MASTER-Tunka | (19h 49m 46.97s , +21d 57m 07.9s) |   C |    10 | 14.6 |        
   12921 | 2025-12-25 23:49:23 |        MASTER-Tunka | (19h 49m 23.66s , +22d 02m 37.8s) |   C |    10 | 15.2 |        
   12921 | 2025-12-25 23:49:23 |        MASTER-Tunka | (19h 49m 41.14s , +21d 56m 09.7s) |   C |    10 | 14.5 |        
   12945 | 2025-12-25 23:49:46 |        MASTER-Tunka | (19h 49m 28.63s , +22d 02m 56.0s) |   C |    10 | 15.1 |        
   12945 | 2025-12-25 23:49:46 |        MASTER-Tunka | (19h 49m 46.21s , +21d 56m 26.8s) |   C |    10 | 14.5 |        
   12972 | 2025-12-25 23:50:13 |        MASTER-Tunka | (19h 49m 26.49s , +22d 04m 32.3s) |   C |    10 | 15.2 |        
   12972 | 2025-12-25 23:50:13 |        MASTER-Tunka | (19h 49m 44.04s , +21d 58m 04.3s) |   C |    10 | 14.5 |        
   12997 | 2025-12-25 23:50:39 |        MASTER-Tunka | (19h 49m 26.25s , +22d 02m 54.0s) |   C |    10 | 15.2 |        
   12997 | 2025-12-25 23:50:39 |        MASTER-Tunka | (19h 49m 43.95s , +21d 56m 23.9s) |   C |    10 | 14.6 |        
   13020 | 2025-12-25 23:51:03 |        MASTER-Tunka | (19h 49m 28.47s , +22d 04m 31.8s) |   C |     5 | 15.0 |        
   13025 | 2025-12-25 23:51:03 |        MASTER-Tunka | (19h 49m 28.47s , +22d 04m 31.7s) |   C |    15 | 15.5 |  Coadd 
   13020 | 2025-12-25 23:51:03 |        MASTER-Tunka | (19h 49m 46.18s , +21d 58m 01.8s) |   C |     5 | 14.4 |        
   13042 | 2025-12-25 23:51:25 |        MASTER-Tunka | (19h 49m 23.36s , +22d 03m 41.2s) |   C |     5 | 14.9 |        
   13042 | 2025-12-25 23:51:25 |        MASTER-Tunka | (19h 49m 42.53s , +21d 57m 20.8s) |   C |     5 | 14.4 |        
   13062 | 2025-12-25 23:51:46 |        MASTER-Tunka | (19h 49m 22.30s , +22d 04m 41.4s) |   C |     5 | 14.9 |        
   13062 | 2025-12-25 23:51:46 |        MASTER-Tunka | (19h 49m 39.99s , +21d 58m 14.0s) |   C |     5 | 14.3 |        
   13080 | 2025-12-25 23:52:03 |        MASTER-Tunka | (19h 49m 28.75s , +22d 03m 40.6s) |   C |     5 | 14.9 |        
   13080 | 2025-12-25 23:52:03 |        MASTER-Tunka | (19h 49m 46.63s , +21d 57m 10.8s) |   C |     5 | 14.4 |        
   13101 | 2025-12-25 23:52:25 |        MASTER-Tunka | (19h 49m 23.26s , +22d 02m 41.2s) |   C |     5 | 15.0 |        
   13101 | 2025-12-25 23:52:25 |        MASTER-Tunka | (19h 49m 41.16s , +21d 56m 11.7s) |   C |     5 | 14.4 |        
   13247 | 2025-12-25 23:54:24 |        MASTER-Tunka | (19h 49m 22.94s , +22d 04m 41.5s) |   C |    60 | 15.5 |        
   13247 | 2025-12-25 23:54:24 |        MASTER-Tunka | (19h 49m 41.00s , +21d 58m 11.0s) |   C |    60 | 14.8 |  Coadd 
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