GCN Circular 42128

Subject
Fermi GRB 251006A: Global MASTER-Net observations report
Event
GRB 251006A
Date
2025-10-06T18:45:52Z (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-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251006A ( Fermi GBM team, GCN 42124Loading...
 
 ) errorbox  16713 sec after notice time and 16748 sec after trigger time at 2025-10-06 18:06:43 UT, with upper limit up to  17.0 mag. The observations began at zenith distance = 42 deg. The sun  altitude  is -18.0 deg. 

The galactic latitude b =  4 deg., longitude l = 12 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3008484

We obtain a following upper limits.  

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

   16778 | 2025-10-06 18:06:43 |         MASTER-SAAO | (17h 34m 02.34s , -16d 58m 33.7s) |   C |    60 | 16.7 |        
   16778 | 2025-10-06 18:06:43 |         MASTER-SAAO | (17h 32m 04.73s , -16d 43m 22.6s) |   C |    60 | 16.8 |        
   16871 | 2025-10-06 18:08:16 |         MASTER-SAAO | (17h 40m 13.62s , -14d 06m 21.6s) |   C |    60 | 16.9 |        
   16871 | 2025-10-06 18:08:16 |         MASTER-SAAO | (17h 38m 17.54s , -13d 51m 10.9s) |   C |    60 | 17.0 |        
Filter C is a clear (unfiltred) band. 


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