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GCN Circular 39640

Subject
Fermi GRB 250309A: Global MASTER-Net observations report
Date
2025-03-09T22:31:05Z (4 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-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250309A ( Fermi GBM team, GCN 39623Loading...
 
 ) errorbox  71845 sec after notice time and 71879 sec after trigger time at 2025-03-09 20:40:03 UT, with upper limit up to  16.2 mag. The observations began at zenith distance = 81 deg. The sun  altitude  is -50.2 deg. 

The galactic latitude b =  0 deg., longitude l = 140 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2805313

We obtain a following upper limits.  

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

   71900 | 2025-03-09 20:40:03 |   MASTER-Kislovodsk | (02h 47m 28.83s , +38d 43m 03.4s) |   C |    40 | 15.5 |        
   71955 | 2025-03-09 20:40:03 |   MASTER-Kislovodsk | (02h 47m 28.84s , +38d 43m 03.3s) |   C |   150 | 16.2 |  Coadd 
   71965 | 2025-03-09 20:41:03 |   MASTER-Kislovodsk | (02h 47m 28.70s , +38d 42m 52.8s) |   C |    50 | 15.4 |        
   72040 | 2025-03-09 20:42:13 |   MASTER-Kislovodsk | (02h 47m 28.63s , +38d 42m 43.8s) |   C |    60 | 15.6 |        
   72130 | 2025-03-09 20:43:33 |   MASTER-Kislovodsk | (02h 47m 28.55s , +38d 42m 35.0s) |   C |    80 | 15.7 |        
   72240 | 2025-03-09 20:43:33 |   MASTER-Kislovodsk | (02h 47m 28.54s , +38d 42m 34.9s) |   C |   300 | 16.1 |  Coadd 
   72240 | 2025-03-09 20:45:13 |   MASTER-Kislovodsk | (02h 47m 28.42s , +38d 42m 25.5s) |   C |   100 | 15.8 |        
   72370 | 2025-03-09 20:47:13 |   MASTER-Kislovodsk | (02h 47m 28.29s , +38d 42m 16.6s) |   C |   120 | 15.7 |        
Filter C is a clear (unfiltred) band. 


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