GCN Circular 42464

Subject
Fermi GRB 251026B: Global MASTER-Net observations report
Event
GRB 251026B
Date
2025-10-27T01:31:39Z (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  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251026B ( Fermi GBM team, GCN 42455Loading...
 
 ) errorbox  59309 sec after notice time and 62633 sec after trigger time at 2025-10-27 00:42:47 UT, with upper limit up to  18.4 mag. The observations began at zenith distance = 68 deg. The sun  altitude  is -32.5 deg. 

The galactic latitude b = 20 deg., longitude l = 239 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3023975

We obtain a following upper limits.  

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

   62664 | 2025-10-27 00:42:47 |   MASTER-Kislovodsk | (08h 46m 04.47s , -11d 51m 14.2s) |   C |    60 | 17.9 |        
   62664 | 2025-10-27 00:42:47 |   MASTER-Kislovodsk | (08h 50m 15.56s , -12d 14m 29.7s) |   C |    60 | 18.3 |        
   63317 | 2025-10-27 00:53:40 |   MASTER-Kislovodsk | (08h 46m 04.23s , -11d 50m 49.0s) |   C |    60 | 17.8 |        
   63317 | 2025-10-27 00:53:40 |   MASTER-Kislovodsk | (08h 50m 17.20s , -12d 14m 14.5s) |   C |    60 | 18.1 |        
   63959 | 2025-10-27 01:04:22 |   MASTER-Kislovodsk | (08h 46m 02.23s , -11d 50m 25.1s) |   C |    60 | 18.2 |        
   63959 | 2025-10-27 01:04:22 |   MASTER-Kislovodsk | (08h 50m 16.29s , -12d 13m 53.6s) |   C |    60 | 18.4 |        
   64626 | 2025-10-27 01:15:29 |   MASTER-Kislovodsk | (08h 46m 09.08s , -11d 49m 58.6s) |   C |    60 | 18.2 |        
   64626 | 2025-10-27 01:15:29 |   MASTER-Kislovodsk | (08h 50m 18.58s , -12d 13m 27.0s) |   C |    60 | 18.4 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.