GCN Circular 41875

Subject
Fermi GRB 250919A: Global MASTER-Net observations report
Event
GRB 250919A
Date
2025-09-19T01:30:59Z (5 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 250919A ( Fermi GBM team, GCN 41874Loading...
 
 ) errorbox  557 sec after notice time and 592 sec after trigger time at 2025-09-19 00:38:44 UT, with upper limit up to  19.3 mag. The observations began at zenith distance = 63 deg. The sun  altitude  is -47.5 deg. 

MASTER-OAFA robotic telescope  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250919A errorbox  658 sec after notice time and 693 sec after trigger time at 2025-09-19 00:40:26 UT, with upper limit up to  20.3 mag. The observations began at zenith distance = 19 deg. The sun  altitude  is -28.7 deg. 

The galactic latitude b = -34 deg., longitude l = 350 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2994728

We obtain a following upper limits.  

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

     622 | 2025-09-19 00:38:44 |         MASTER-SAAO | (20h 12m 52.30s , -49d 54m 57.2s) |   C |    60 | 19.3 |        
     622 | 2025-09-19 00:38:44 |         MASTER-SAAO | (20h 10m 02.82s , -49d 39m 38.7s) |   C |    60 | 19.2 |        
     764 | 2025-09-19 00:40:26 |         MASTER-OAFA | (20h 13m 10.49s , -49d 55m 27.8s) |   C |   140 | 20.2 |        
     925 | 2025-09-19 00:42:52 |         MASTER-OAFA | (20h 13m 10.79s , -49d 55m 23.7s) |   C |   170 | 20.3 |        
Filter C is a clear (unfiltred) band. 


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