GCN Circular 42504

Subject
Fermi GRB 251028B: Global MASTER-Net observations report
Event
GRB 251028B
Date
2025-10-28T14:00:39Z (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-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251028B ( Fermi GBM team, GCN 42502Loading...
 
 ) errorbox  19936 sec after notice time and 19967 sec after trigger time at 2025-10-28 13:20:54 UT, with upper limit up to  18.6 mag. The observations began at zenith distance =  6 deg. The sun  altitude  is -33.5 deg. 

The galactic latitude b = -10 deg., longitude l = 99 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3025691

We obtain a following upper limits.  

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

   19998 | 2025-10-28 13:20:54 |        MASTER-Tunka | (22h 31m 44.47s , +45d 04m 55.7s) |   C |    60 | 18.6 |        
   19998 | 2025-10-28 13:20:54 |             MASTER- | (22h 30m 56.32s , +45d 13m 01.0s) |   C |    60 | 18.3 |        
   20070 | 2025-10-28 13:22:06 |        MASTER-Tunka | (22h 34m 25.03s , +46d 58m 00.3s) |   C |    60 | 17.5 |        
   20070 | 2025-10-28 13:22:06 |             MASTER- | (22h 33m 35.14s , +47d 06m 10.6s) |   C |    60 | 17.3 |        
   20146 | 2025-10-28 13:23:22 |        MASTER-Tunka | (22h 30m 48.12s , +43d 08m 44.4s) |   C |    60 | 13.9 |        
Filter C is a clear (unfiltred) band. 


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