GCN Circular 44708

Subject
Fermi GRB 260526A: Global MASTER-Net observations report
Event
GRB 260526A
Date
2026-05-27T00:32:25Z (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),
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) started inspect of the Fermi GRB 260526A ( Fermi GBM team, GCN 44707Loading...
 
 ) errorbox  872 sec after notice time and 1002 sec after trigger time at 2026-05-26 23:20:42 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 79 deg. The sun  altitude  is -20.1 deg. 

The galactic latitude b = -14 deg., longitude l = 143 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3341266

We obtain a following upper limits.  

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

    1032 | 2026-05-26 23:20:42 |      MASTER-Tavrida | (02h 40m 21.49s , +46d 38m 05.4s) |   C |    60 | 14.9 |        
    1113 | 2026-05-26 23:22:03 |      MASTER-Tavrida | (02h 25m 12.72s , +46d 35m 35.0s) |   C |    60 | 12.0 |        
    3275 | 2026-05-26 23:58:05 |      MASTER-Tavrida | (02h 32m 55.74s , +43d 58m 52.2s) |   C |    60 | 16.5 |        
    4690 | 2026-05-27 00:21:40 |      MASTER-Tavrida | (02h 36m 20.55s , +45d 17m 15.2s) |   C |    60 | 16.8 |        
    4769 | 2026-05-27 00:22:59 |      MASTER-Tavrida | (02h 15m 28.16s , +42d 39m 11.4s) |   C |    60 | 17.1 |        
    4848 | 2026-05-27 00:24:17 |      MASTER-Tavrida | (02h 12m 43.82s , +41d 19m 58.6s) |   C |    60 | 16.9 |        
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