GCN Circular 42390

Subject
Fermi GRB 251023A: Global MASTER-Net observations report
Event
GRB 251023A
Date
2025-10-23T09:15:24Z (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-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 251023A ( Fermi GBM team, GCN 42385Loading...
 
 ) errorbox  665 sec after notice time and 686 sec after trigger time at 2025-10-23 06:09:10 UT, with upper limit up to  20.7 mag. The observations began at zenith distance = 29 deg. The sun  altitude  is -40.0 deg. 

The galactic latitude b = -56 deg., longitude l = 180 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3021658

We obtain a following upper limits.  

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

     717 | 2025-10-23 06:09:10 |         MASTER-OAFA | (02h 36m 41.44s , -06d 42m 24.3s) |   C |    60 | 20.6 |        
     792 | 2025-10-23 06:10:25 |         MASTER-OAFA | (02h 36m 48.65s , -06d 42m 09.1s) |   C |    60 | 20.6 |        
     880 | 2025-10-23 06:11:53 |         MASTER-OAFA | (02h 51m 27.06s , -04d 47m 02.9s) |   C |    60 | 20.4 |        
     956 | 2025-10-23 06:13:09 |         MASTER-OAFA | (02h 51m 25.90s , -04d 46m 08.3s) |   C |    60 | 20.4 |        
    1045 | 2025-10-23 06:14:38 |         MASTER-OAFA | (02h 29m 25.20s , -08d 34m 50.8s) |   C |    60 | 20.3 |        
    1120 | 2025-10-23 06:15:53 |         MASTER-OAFA | (02h 37m 24.96s , -08d 34m 57.2s) |   C |    60 | 20.4 |        
    1197 | 2025-10-23 06:17:10 |         MASTER-OAFA | (02h 29m 18.79s , -08d 34m 44.5s) |   C |    60 | 20.3 |        
    1272 | 2025-10-23 06:18:25 |         MASTER-OAFA | (02h 37m 30.89s , -08d 35m 06.2s) |   C |    60 | 20.4 |        
    1353 | 2025-10-23 06:19:46 |         MASTER-OAFA | (02h 44m 42.03s , -08d 34m 33.8s) |   C |    60 | 20.6 |        
    1429 | 2025-10-23 06:21:02 |         MASTER-OAFA | (02h 52m 48.50s , -08d 32m 57.2s) |   C |    60 | 20.5 |        
    1503 | 2025-10-23 06:22:16 |         MASTER-OAFA | (02h 44m 48.52s , -08d 34m 42.6s) |   C |    60 | 20.7 |        
    1579 | 2025-10-23 06:23:32 |         MASTER-OAFA | (02h 52m 49.17s , -08d 35m 05.7s) |   C |    60 | 20.4 |        
    1654 | 2025-10-23 06:24:47 |         MASTER-OAFA | (02h 44m 47.30s , -08d 35m 42.7s) |   C |    60 | 20.6 |        
    1733 | 2025-10-23 06:26:07 |         MASTER-OAFA | (02h 52m 04.95s , -06d 40m 17.4s) |   C |    60 | 20.2 |        
    1895 | 2025-10-23 06:28:48 |         MASTER-OAFA | (02h 51m 58.29s , -06d 40m 20.1s) |   C |    60 | 20.2 |        
    1981 | 2025-10-23 06:30:14 |         MASTER-OAFA | (02h 30m 14.33s , -10d 30m 32.8s) |   C |    60 | 20.2 |        
    2057 | 2025-10-23 06:31:30 |         MASTER-OAFA | (02h 38m 20.88s , -10d 28m 16.3s) |   C |    60 | 20.5 |        
    2132 | 2025-10-23 06:32:45 |         MASTER-OAFA | (02h 38m 22.92s , -10d 28m 22.0s) |   C |    60 | 20.4 |        
    2215 | 2025-10-23 06:34:08 |         MASTER-OAFA | (02h 59m 21.23s , -06d 41m 00.5s) |   C |    60 | 20.0 |        
    2369 | 2025-10-23 06:36:42 |         MASTER-OAFA | (02h 59m 20.42s , -06d 42m 09.2s) |   C |    60 | 20.1 |        
    3339 | 2025-10-23 06:52:52 |         MASTER-OAFA | (02h 39m 52.78s , -06d 23m 46.0s) |   C |    60 | 19.5 |        
    3405 | 2025-10-23 06:53:58 |         MASTER-OAFA | (02h 39m 52.75s , -06d 23m 44.1s) |   C |    60 | 19.5 |        
    3470 | 2025-10-23 06:55:03 |         MASTER-OAFA | (02h 39m 52.71s , -06d 23m 42.5s) |   C |    60 | 19.6 |        
    3536 | 2025-10-23 06:56:09 |         MASTER-OAFA | (02h 39m 52.68s , -06d 23m 41.2s) |   C |    60 | 20.6 |        
    3601 | 2025-10-23 06:57:15 |         MASTER-OAFA | (02h 39m 52.66s , -06d 23m 39.7s) |   C |    60 | 20.6 |        
    3667 | 2025-10-23 06:58:20 |         MASTER-OAFA | (02h 39m 52.65s , -06d 23m 38.5s) |   C |    60 | 20.6 |        
    3734 | 2025-10-23 06:59:27 |         MASTER-OAFA | (02h 39m 52.64s , -06d 23m 37.5s) |   C |    60 | 20.6 |        
    3800 | 2025-10-23 07:00:33 |         MASTER-OAFA | (02h 39m 52.62s , -06d 23m 36.4s) |   C |    60 | 20.5 |        
    3865 | 2025-10-23 07:01:38 |         MASTER-OAFA | (02h 39m 52.61s , -06d 23m 35.4s) |   C |    60 | 20.5 |        
    3931 | 2025-10-23 07:02:44 |         MASTER-OAFA | (02h 39m 52.60s , -06d 23m 34.4s) |   C |    60 | 20.4 |        
    3997 | 2025-10-23 07:03:50 |         MASTER-OAFA | (02h 39m 52.60s , -06d 23m 33.5s) |   C |    60 | 20.5 |        
    4063 | 2025-10-23 07:04:56 |         MASTER-OAFA | (02h 39m 52.59s , -06d 23m 32.6s) |   C |    60 | 20.6 |        
Filter C is a clear (unfiltred) band. 


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