GCN Circular 44700

Subject
Fermi GRB 260523A: Global MASTER-Net observations report
Event
GRB 260523A
Date
2026-05-23T23:46:05Z (6 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) started inspect of the Fermi GRB 260523A ( Fermi GBM team, GCN 44698Loading...
 
 ) errorbox  26626 sec after notice time and 26682 sec after trigger time at 2026-05-23 23:30:53 UT, with upper limit up to  18.5 mag. The observations began at zenith distance = 61 deg. The sun  altitude  is -17.4 deg. 

The galactic latitude b = -33 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=3334230

We obtain a following upper limits.  

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

   26713 | 2026-05-23 23:30:53 |   MASTER-Kislovodsk | (21h 01m 49.35s , -06d 30m 25.4s) |   C |    60 | 18.3 |        
   26812 | 2026-05-23 23:32:32 |   MASTER-Kislovodsk | (20h 55m 10.53s , -08d 23m 36.1s) |   C |    60 | 18.4 |        
   26911 | 2026-05-23 23:34:11 |   MASTER-Kislovodsk | (20h 49m 48.74s , -06d 27m 51.5s) |   C |    60 | 18.1 |        
   27006 | 2026-05-23 23:35:46 |   MASTER-Kislovodsk | (20h 58m 00.72s , -04d 36m 04.2s) |   C |    60 | 18.3 |        
   27235 | 2026-05-23 23:39:35 |   MASTER-Kislovodsk | (21h 07m 20.43s , -08d 24m 37.0s) |   C |    60 | 18.5 |        
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