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GCN Circular 39694

Subject
Fermi GRB 250312B: Global MASTER-Net observations report
Date
2025-03-12T22:15:40Z (a day 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 250312B ( Fermi GBM team, GCN 39692Loading...
 
 ) errorbox  1617 sec after notice time and 1650 sec after trigger time at 2025-03-12 21:04:27 UT, with upper limit up to  18.4 mag. The observations began at zenith distance = 25 deg. The sun  altitude  is -47.1 deg. 

The galactic latitude b = 11 deg., longitude l = 296 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2810182

We obtain a following upper limits.  

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

    1681 | 2025-03-12 21:04:27 |         MASTER-SAAO | (11h 29m 04.39s , -48d 18m 30.7s) |   C |    60 | 18.2 |        
    3030 | 2025-03-12 21:26:57 |         MASTER-SAAO | (11h 29m 01.89s , -48d 17m 08.7s) |   C |    60 | 18.2 |        
    3110 | 2025-03-12 21:28:16 |         MASTER-SAAO | (12h 02m 31.64s , -51d 04m 13.5s) |   C |    60 | 18.0 |        
    3170 | 2025-03-12 21:28:16 |         MASTER-SAAO | (12h 02m 31.64s , -51d 04m 13.5s) |   C |   180 | 18.4 |  Coadd 
    3189 | 2025-03-12 21:29:35 |         MASTER-SAAO | (12h 02m 31.65s , -51d 04m 13.4s) |   C |    60 | 17.9 |        
    3268 | 2025-03-12 21:30:54 |         MASTER-SAAO | (12h 02m 31.60s , -51d 04m 13.0s) |   C |    60 | 17.9 |        
    3347 | 2025-03-12 21:32:13 |         MASTER-SAAO | (12h 02m 31.51s , -51d 04m 12.3s) |   C |    60 | 17.9 |        
Filter C is a clear (unfiltred) band. 


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