GCN Circular 42235

Subject
Fermi GRB 251013C: Global MASTER-Net observations report
Event
GRB 251013C
Date
2025-10-13T23:46:00Z (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 251013C ( Fermi GBM team, GCN 42221Loading...
 
 ) errorbox  10000 sec after notice time and 10034 sec after trigger time at 2025-10-13 20:26:56 UT, with upper limit up to  20.4 mag. The observations began at zenith distance = 32 deg. The sun  altitude  is -41.1 deg. 

The galactic latitude b = -59 deg., longitude l = 72 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3013941

We obtain a following upper limits.  

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

   10064 | 2025-10-13 20:26:56 |         MASTER-SAAO | (23h 02m 39.24s , -00d 30m 39.4s) |   C |    60 | 18.6 |        
   10158 | 2025-10-13 20:28:29 |         MASTER-SAAO | (23h 02m 46.41s , -00d 31m 36.1s) |   C |    60 | 18.7 |        
   10251 | 2025-10-13 20:30:02 |         MASTER-SAAO | (23h 02m 40.37s , -00d 32m 32.6s) |   C |    60 | 18.9 |        
   10345 | 2025-10-13 20:31:37 |         MASTER-SAAO | (23h 02m 47.55s , -00d 32m 05.9s) |   C |    60 | 18.8 |        
   10441 | 2025-10-13 20:33:12 |         MASTER-SAAO | (23h 02m 45.46s , -00d 30m 49.0s) |   C |    60 | 18.7 |        
   10539 | 2025-10-13 20:34:50 |         MASTER-SAAO | (23h 02m 46.25s , -00d 32m 02.3s) |   C |    60 | 18.6 |        
   10664 | 2025-10-13 20:36:25 |         MASTER-SAAO | (23h 02m 49.67s , -00d 30m 22.6s) |   C |   120 | 18.9 |        
   10817 | 2025-10-13 20:38:58 |         MASTER-SAAO | (23h 02m 45.08s , -00d 31m 17.6s) |   C |   120 | 18.8 |        
   10980 | 2025-10-13 20:41:42 |         MASTER-SAAO | (23h 02m 47.31s , -00d 30m 13.8s) |   C |   120 | 19.0 |        
   11135 | 2025-10-13 20:44:17 |         MASTER-SAAO | (23h 02m 52.66s , -00d 31m 09.8s) |   C |   120 | 19.0 |        
   11292 | 2025-10-13 20:46:54 |         MASTER-SAAO | (23h 02m 47.94s , -00d 32m 05.5s) |   C |   120 | 19.2 |        
   11446 | 2025-10-13 20:49:27 |         MASTER-SAAO | (23h 02m 55.30s , -00d 32m 00.3s) |   C |   120 | 19.2 |        
   11630 | 2025-10-13 20:52:01 |         MASTER-SAAO | (23h 02m 53.52s , -00d 30m 03.7s) |   C |   180 | 19.2 |        
   11847 | 2025-10-13 20:55:39 |         MASTER-SAAO | (23h 02m 54.71s , -00d 31m 32.8s) |   C |   180 | 19.2 |        
   12064 | 2025-10-13 20:59:15 |         MASTER-SAAO | (23h 02m 58.96s , -00d 29m 55.7s) |   C |   180 | 19.4 |        
   12247 | 2025-10-13 21:02:48 |         MASTER-SAAO | (23h 02m 53.36s , -00d 30m 39.0s) |   C |   120 | 19.4 |        
   12399 | 2025-10-13 21:05:21 |         MASTER-SAAO | (23h 02m 55.07s , -00d 29m 35.0s) |   C |   120 | 19.4 |        
   12519 | 2025-10-13 21:05:21 |         MASTER-SAAO | (23h 02m 55.07s , -00d 29m 35.0s) |   C |   360 | 20.1 |  Coadd 
   12554 | 2025-10-13 21:07:55 |         MASTER-SAAO | (23h 03m 01.04s , -00d 30m 30.6s) |   C |   120 | 19.4 |        
   12722 | 2025-10-13 21:10:43 |         MASTER-SAAO | (23h 02m 55.49s , -00d 31m 25.3s) |   C |   120 | 19.7 |        
   12875 | 2025-10-13 21:13:16 |         MASTER-SAAO | (23h 03m 01.00s , -00d 31m 12.9s) |   C |   120 | 19.4 |        
   12995 | 2025-10-13 21:13:16 |         MASTER-SAAO | (23h 03m 01.00s , -00d 31m 12.9s) |   C |   360 | 20.4 |  Coadd 
   13030 | 2025-10-13 21:15:51 |         MASTER-SAAO | (23h 02m 59.29s , -00d 29m 35.6s) |   C |   120 | 19.7 |        
   13194 | 2025-10-13 21:18:36 |         MASTER-SAAO | (23h 02m 59.68s , -00d 30m 53.7s) |   C |   120 | 19.6 |        
   13347 | 2025-10-13 21:21:09 |         MASTER-SAAO | (23h 03m 02.87s , -00d 29m 15.8s) |   C |   120 | 19.9 |        
   13502 | 2025-10-13 21:23:44 |         MASTER-SAAO | (23h 02m 57.06s , -00d 30m 00.8s) |   C |   120 | 19.8 |        
   16491 | 2025-10-13 22:14:02 |         MASTER-SAAO | (23h 07m 20.08s , -06d 42m 29.2s) |   C |    60 | 18.9 |        
Filter C is a clear (unfiltred) band. 


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