GCN Circular 43322

Subject
Swift GRB 260104A: Global MASTER-Net observations report
Event
GRB 260104A
Date
2026-01-04T16:48:28Z (4 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-Kislovodsk robotic telescope  [1]  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 260104A ( R. Caputo et al., GCN 43315Loading...
 
 ) errorbox  39152 sec after notice time and 39173 sec after trigger time at 2026-01-04 16:29:55 UT, with upper limit up to  15.0 mag. The observations began at zenith distance = 82 deg. The sun  altitude  is -28.6 deg. 

The galactic latitude b = -58 deg., longitude l = 36 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3095622

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   39263 |   MASTER-Kislovodsk |   C |   180 | 13.5 |        
   39263 |   MASTER-Kislovodsk |   C |   180 | 14.3 |        
   39471 |   MASTER-Kislovodsk |   C |   180 | 13.5 |        
   39471 |   MASTER-Kislovodsk |   C |   180 | 14.1 |        
   39687 |   MASTER-Kislovodsk |   C |   180 | 14.2 |        
   39687 |   MASTER-Kislovodsk |   C |   180 | 15.0 |        
   39903 |   MASTER-Kislovodsk |   C |   180 | 14.7 |        
   39903 |   MASTER-Kislovodsk |   C |   180 | 15.0 |        
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