GCN Circular 42233

Subject
Fermi GRB 251013D: Global MASTER-Net observations report
Event
GRB 251013D
Date
2025-10-13T22:31:33Z (7 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 251013D ( Fermi GBM team, GCN 42224Loading...
 
 ) errorbox  12470 sec after notice time and 12506 sec after trigger time at 2025-10-13 21:45:26 UT, with upper limit up to  19.2 mag. The observations began at zenith distance = 54 deg. The sun  altitude  is -48.9 deg. 

The galactic latitude b = -41 deg., longitude l = 167 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3013985

We obtain a following upper limits.  

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

   12536 | 2025-10-13 21:45:26 |         MASTER-SAAO | (02h 43m 45.87s , +12d 29m 46.5s) |   C |    60 | 18.9 |        
   12536 | 2025-10-13 21:45:26 |         MASTER-SAAO | (02h 45m 35.22s , +12d 14m 30.3s) |   C |    60 | 19.0 |        
   12729 | 2025-10-13 21:48:39 |         MASTER-SAAO | (02h 42m 32.93s , +10d 34m 14.1s) |   C |    60 | 19.1 |        
   12729 | 2025-10-13 21:48:39 |         MASTER-SAAO | (02h 44m 21.71s , +10d 18m 58.2s) |   C |    60 | 19.2 |        
Filter C is a clear (unfiltred) band. 


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