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GCN Circular 39991

Subject
Fermi GRB 250331E: Global MASTER-Net observations report
Date
2025-04-01T01:16:06Z (12 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 250331E ( Fermi GBM team, GCN 39988Loading...
 
 ) errorbox 4 sec after trigger time at 2025-03-31 22:46:37 UT, with upper limit up to  19.3 mag. The observations began at zenith distance = 12 deg. The sun  altitude  is -62.4 deg. 

The galactic latitude b = 35 deg., longitude l = 308 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2829592

We obtain a following upper limits.  

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

      35 | 2025-03-31 22:46:37 |         MASTER-SAAO | (12h 57m 48.00s , -20d 04m 42.7s) |   C |    60 | 19.0 |        
     114 | 2025-03-31 22:47:56 |         MASTER-SAAO | (13h 06m 14.94s , -20d 06m 25.5s) |   C |    60 | 19.1 |        
    1229 | 2025-03-31 23:06:32 |         MASTER-SAAO | (13h 25m 08.68s , -32d 04m 39.4s) |   C |    60 | 19.0 |        
    1388 | 2025-03-31 23:09:10 |         MASTER-SAAO | (13h 34m 31.38s , -32d 07m 08.5s) |   C |    60 | 19.2 |        
    2434 | 2025-03-31 23:26:37 |         MASTER-SAAO | (13h 25m 13.32s , -32d 05m 29.0s) |   C |    60 | 19.2 |        
    2593 | 2025-03-31 23:29:15 |         MASTER-SAAO | (14h 07m 32.41s , -36d 55m 59.7s) |   C |    60 | 19.3 |        
    3468 | 2025-03-31 23:43:50 |         MASTER-SAAO | (14h 07m 42.96s , -36d 54m 45.6s) |   C |    60 | 19.1 |        
    4282 | 2025-03-31 23:57:24 |         MASTER-SAAO | (14h 07m 44.51s , -36d 53m 28.5s) |   C |    60 | 19.1 |        
    5764 | 2025-04-01 00:22:06 |         MASTER-SAAO | (14h 07m 53.30s , -36d 53m 01.5s) |   C |    60 | 19.1 |        
    6499 | 2025-04-01 00:34:21 |         MASTER-SAAO | (14h 07m 57.57s , -36d 54m 12.1s) |   C |    60 | 19.2 |        
    7157 | 2025-04-01 00:45:19 |         MASTER-SAAO | (14h 07m 59.18s , -36d 53m 44.9s) |   C |    60 | 19.1 |        
    7236 | 2025-04-01 00:46:38 |         MASTER-SAAO | (13h 35m 38.73s , -27d 21m 54.8s) |   C |    60 | 19.1 |        
    7315 | 2025-04-01 00:47:58 |         MASTER-SAAO | (13h 44m 37.58s , -27d 21m 15.5s) |   C |    60 | 19.3 |        
    7474 | 2025-04-01 00:50:36 |         MASTER-SAAO | (13h 22m 32.82s , -25d 27m 53.6s) |   C |    60 | 19.3 |        
Filter C is a clear (unfiltred) band. 


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