GCN Circular 43219

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 EP251222a ( EP Team et al., GCN 43200
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 ) errorbox  25213 sec after notice time and 69548 sec after trigger time at 2025-12-23 10:37:14 UT, with upper limit up to  16.4 mag. Observations started at twilight.  The observations began at zenith distance = 78 deg. The sun  altitude  is -13.8 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251222a errorbox  39747 sec after notice time and 84082 sec after trigger time at 2025-12-23 14:39:28 UT, with upper limit up to  16.9 mag. Observations started at twilight.  The observations began at zenith distance = 75 deg. The sun  altitude  is -10.5 deg. 

The galactic latitude b = -35 deg., longitude l = 194 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3081644

We obtain a following upper limits.  

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

   66002 | 2025-12-23 09:36:37 |             MASTER- | (04h 15m 01.67s , -00d 43m 08.5s) |   C |   180 | 16.3 |        
   69578 | 2025-12-23 10:37:14 |        MASTER-Tunka | (04h 09m 44.57s , -01d 55m 17.1s) |   C |    60 | 16.4 |        
   69578 | 2025-12-23 10:37:14 |        MASTER-Tunka | (04h 09m 58.83s , -02d 01m 41.0s) |   C |    60 | 16.1 |        
   69649 | 2025-12-23 10:38:24 |        MASTER-Tunka | (04h 09m 58.86s , -02d 01m 41.4s) |   C |    60 | 15.7 |        
   69649 | 2025-12-23 10:38:25 |        MASTER-Tunka | (04h 09m 44.41s , -01d 55m 16.5s) |   C |    60 | 16.1 |        
   84112 | 2025-12-23 14:39:28 |   MASTER-Kislovodsk | (04h 07m 57.86s , -01d 42m 13.8s) |   C |    60 | 16.9 |        
   84112 | 2025-12-23 14:39:28 |   MASTER-Kislovodsk | (04h 07m 58.58s , -01d 19m 40.7s) |   C |    60 | 15.8 |        
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