GCN Circular 44824

Subject
SVOM GRB260604.85: Global MASTER-Net observations report
Event
GRB 260604.85
Date
2026-06-04T20:48:54Z (3 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),
M. Segura,  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 SVOM GRB260604.85 (trigger No 1780604437,14h 57m 12.77s , +28d 36m 26.6s, R=0.1738) errorbox  43 sec after notice time and 713 sec after trigger time at 2026-06-04 20:32:30 UT, with upper limit up to  19.4 mag. The observations began at zenith distance = 18 deg. The sun  altitude  is -21.0 deg. 

The galactic latitude b = 62 deg., longitude l = 43 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3361056

We obtain a following upper limits.  

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

     774 | 2026-06-04 20:32:30 |      MASTER-Tavrida | (14h 57m 09.62s , +29d 05m 58.4s) |   C |   120 | 19.4 |        
     897 | 2026-06-04 20:34:33 |      MASTER-Tavrida | (14h 57m 09.73s , +29d 05m 54.0s) |   C |   120 | 19.4 |        
    1019 | 2026-06-04 20:36:36 |      MASTER-Tavrida | (14h 57m 09.83s , +29d 05m 50.2s) |   C |   120 | 19.4 |        
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