GCN Circular 42381

Subject

LAT GRB251022A: Global MASTER-Net observations report

Event

GRB 251022A

Date

2025-10-23T03:11:21Z (2 days ago)

Edited On

2025-10-23T22:16:23Z (17 hours ago)

From

Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

Edited By

Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Vladimir Lipunov at Lomonosov Moscow State University <lipunov@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) was pointed to the LAT GRB251022.94 (trigger No 782865260,04h 21m 31.18s , -19d 18m 35.6s, R=0.32) errorbox  13 sec after notice time and 16215 sec after trigger time at 2025-10-23 03:04:30 UT, with upper limit up to  17.2 mag. Observations started at twilight.  The observations began at zenith distance = 32 deg. The sun  altitude  is -10.1 deg. 

The galactic latitude b = -41 deg., longitude l = 216 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3021522

We obtain a following upper limits.  

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

   16245 | 2025-10-23 03:04:30 |         MASTER-SAAO | (04h 21m 02.62s , -19d 31m 07.4s) |   C |    60 | 17.2 |        
   16245 | 2025-10-23 03:04:30 |         MASTER-SAAO | (04h 19m 05.26s , -19d 15m 42.2s) |  P\ |    60 | 16.7 |        
   16324 | 2025-10-23 03:05:49 |         MASTER-SAAO | (04h 21m 02.39s , -19d 31m 03.5s) |   C |    60 | 16.7 |        
   16324 | 2025-10-23 03:05:49 |         MASTER-SAAO | (04h 19m 05.05s , -19d 15m 37.8s) |  P\ |    60 | 16.6 |        
   16404 | 2025-10-23 03:07:08 |         MASTER-SAAO | (04h 19m 04.85s , -19d 15m 33.5s) |  P\ |    60 | 16.6 |        
Filter C is a clear (unfiltred) band. 


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