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GCN Circular 40035

Subject
Fermi GRB 250403A: Global MASTER-Net observations report
Date
2025-04-03T21:47:38Z (15 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
V.Lipunov, E.Gorbovskoy, N.Tiurina,  P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov,  G.Antipov,  A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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 250403A ( Fermi GBM team, GCN 40025Loading...
 
 ) errorbox  22256 sec after notice time and 22291 sec after trigger time at 2025-04-03 21:26:53 UT, with upper limit up to  18.5 mag. The observations began at zenith distance = 27 deg. The sun  altitude  is -58.3 deg. 

The galactic latitude b = 36 deg., longitude l = 316 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2832003

We obtain a following upper limits.  

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

   22321 | 2025-04-03 21:26:53 |         MASTER-SAAO | (13h 38m 33.90s , -25d 30m 56.0s) |   C |    60 | 18.5 |        
   22400 | 2025-04-03 21:28:13 |         MASTER-SAAO | (13h 47m 18.63s , -25d 31m 56.8s) |   C |    60 | 18.4 |        
   22559 | 2025-04-03 21:30:51 |         MASTER-SAAO | (13h 34m 56.63s , -27d 26m 34.6s) |   C |    60 | 18.4 |        
Filter C is a clear (unfiltred) band. 


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