TITLE: GCN CIRCULAR NUMBER: 39980 SUBJECT: Swift GRB 250331B: Global MASTER-Net observations report DATE: 25/03/31 17:47:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs lipunov@xray.sai.msu.ru
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) was pointed to the Swift GRB 250331B ( S. B. Cenko et al., GCN 39958) errorbox 47556 sec after notice time and 47612 sec after trigger time at 2025-03-31 17:33:15 UT, with upper limit up to 16.9 mag. Observations started at twilight. The observations began at zenith distance = 85 deg. The sun altitude is -13.0 deg.
The galactic latitude b = -1 deg., longitude l = 161 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2828939
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________
47702 | MASTER-SAAO | C | 180 | 16.5 | 47902 | MASTER-SAAO | C | 180 | 16.7 | 48101 | MASTER-SAAO | C | 180 | 16.9 | Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
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