GCN Circular 41840

Subject
Fermi GRB 250916A: Global MASTER-Net observations report
Event
GRB 250916A
Date
2025-09-16T15:30:58Z (6 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-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250916A ( Fermi GBM team, GCN 41839Loading...
 
 ) errorbox  2134 sec after notice time and 2165 sec after trigger time at 2025-09-16 14:05:26 UT, with upper limit up to  20.8 mag. The observations began at zenith distance = 44 deg. The sun  altitude  is -24.7 deg. 

The galactic latitude b = -20 deg., longitude l = 137 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2992979

We obtain a following upper limits.  

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

    2196 | 2025-09-16 14:05:26 |        MASTER-Tunka | (01h 01m 35.41s , +42d 32m 50.5s) |   C |    60 | 20.7 |        
    2196 | 2025-09-16 14:05:26 |             MASTER- | (01h 02m 07.93s , +42d 25m 57.0s) |   C |    60 | 20.5 |        
    2271 | 2025-09-16 14:06:42 |        MASTER-Tunka | (01h 31m 07.38s , +48d 15m 08.4s) |   C |    60 | 19.6 |        
    2271 | 2025-09-16 14:06:42 |             MASTER- | (01h 31m 43.29s , +48d 08m 17.2s) |   C |    60 | 19.5 |        
    2825 | 2025-09-16 14:15:56 |        MASTER-Tunka | (01h 01m 37.13s , +42d 32m 44.7s) |   C |    60 | 20.6 |        
    2825 | 2025-09-16 14:15:56 |             MASTER- | (01h 02m 10.56s , +42d 25m 34.6s) |   C |    60 | 20.6 |        
    2900 | 2025-09-16 14:17:11 |        MASTER-Tunka | (01h 31m 06.83s , +48d 15m 06.1s) |   C |    60 | 20.2 |        
    2900 | 2025-09-16 14:17:11 |             MASTER- | (01h 31m 43.65s , +48d 07m 58.6s) |   C |    60 | 19.8 |        
    4244 | 2025-09-16 14:39:34 |        MASTER-Tunka | (01h 17m 38.67s , +38d 43m 55.2s) |   C |    60 | 19.8 |        
    4244 | 2025-09-16 14:39:34 |             MASTER- | (01h 18m 09.42s , +38d 37m 35.4s) |   C |    60 | 19.7 |        
    4985 | 2025-09-16 14:51:56 |        MASTER-Tunka | (01h 01m 35.37s , +42d 30m 26.2s) |   C |    60 | 20.7 |        
    4985 | 2025-09-16 14:51:56 |             MASTER- | (01h 02m 11.14s , +42d 22m 49.2s) |   C |    60 | 20.6 |        
    5059 | 2025-09-16 14:53:10 |        MASTER-Tunka | (01h 31m 07.69s , +48d 15m 07.8s) |   C |    60 | 20.2 |        
    5059 | 2025-09-16 14:53:10 |             MASTER- | (01h 31m 47.54s , +48d 07m 33.5s) |   C |    60 | 19.9 |        
    5553 | 2025-09-16 15:01:23 |        MASTER-Tunka | (01h 17m 43.01s , +38d 42m 15.8s) |   C |    60 | 19.8 |        
    5553 | 2025-09-16 15:01:23 |             MASTER- | (01h 18m 15.41s , +38d 35m 49.9s) |   C |    60 | 19.7 |        
    5775 | 2025-09-16 15:05:05 |        MASTER-Tunka | (01h 01m 31.47s , +42d 30m 13.1s) |   C |    60 | 20.8 |        
    5775 | 2025-09-16 15:05:06 |             MASTER- | (01h 02m 08.39s , +42d 23m 51.2s) |   C |    60 | 20.6 |        
    5852 | 2025-09-16 15:06:22 |        MASTER-Tunka | (01h 31m 05.98s , +48d 12m 03.1s) |   C |    60 | 20.3 |        
    5852 | 2025-09-16 15:06:22 |             MASTER- | (01h 31m 46.96s , +48d 05m 44.0s) |   C |    60 | 19.9 |        
    6285 | 2025-09-16 15:13:36 |        MASTER-Tunka | (01h 17m 33.49s , +38d 39m 54.6s) |   C |    60 | 19.9 |        
    6285 | 2025-09-16 15:13:36 |             MASTER- | (01h 18m 04.22s , +38d 34m 21.2s) |   C |    60 | 19.7 |        
    6508 | 2025-09-16 15:17:18 |        MASTER-Tunka | (01h 01m 28.89s , +42d 27m 40.0s) |   C |    60 | 20.7 |        
    6508 | 2025-09-16 15:17:18 |             MASTER- | (01h 02m 05.60s , +42d 21m 48.9s) |   C |    60 | 20.7 |        
    6582 | 2025-09-16 15:18:33 |        MASTER-Tunka | (01h 31m 05.87s , +48d 12m 44.6s) |   C |    60 | 19.7 |        
    6582 | 2025-09-16 15:18:33 |             MASTER- | (01h 31m 46.70s , +48d 06m 57.1s) |   C |    60 | 19.6 |        
Filter C is a clear (unfiltred) band. 


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