GCN Circular 42310

Subject
Fermi GRB 251016A: Global MASTER-Net observations report
Event
GRB 251016A
Date
2025-10-16T19:00:45Z (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-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 251016A ( Fermi GBM team, GCN 42309Loading...
 
 ) errorbox  9753 sec after notice time and 9784 sec after trigger time at 2025-10-16 17:42:24 UT, with upper limit up to  16.8 mag. Observations started at twilight.  The observations began at zenith distance = 38 deg. The sun  altitude  is -11.4 deg. 

The galactic latitude b = -12 deg., longitude l = 344 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3016116

We obtain a following upper limits.  

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

    9814 | 2025-10-16 17:42:24 |         MASTER-SAAO | (17h 41m 59.48s , -48d 04m 09.1s) |   C |    60 | 14.4 |        
    9814 | 2025-10-16 17:42:24 |         MASTER-SAAO | (17h 44m 44.95s , -48d 19m 26.1s) |   C |    60 | 16.5 |        
    9909 | 2025-10-16 17:43:58 |         MASTER-SAAO | (17h 39m 01.22s , -50d 11m 14.5s) |   C |    60 | 16.8 |        
    9909 | 2025-10-16 17:43:58 |         MASTER-SAAO | (17h 36m 07.40s , -49d 55m 40.2s) |   C |    60 | 15.2 |        
   10004 | 2025-10-16 17:45:33 |         MASTER-SAAO | (17h 48m 32.79s , -46d 10m 37.6s) |   C |    60 | 14.6 |        
   10004 | 2025-10-16 17:45:33 |         MASTER-SAAO | (17h 51m 12.71s , -46d 25m 54.6s) |   C |    60 | 16.6 |        
Filter C is a clear (unfiltred) band. 


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