TITLE: GCN CIRCULAR NUMBER: 40594 SUBJECT: Fermi GRB 250531A: Global MASTER-Net observations report DATE: 25/05/31 19:31:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs lipunov@xray.sai.msu.ru
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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 250531A ( Fermi GBM team, GCN 40593) errorbox 1696 sec after notice time and 1758 sec after trigger time at 2025-05-31 18:31:43 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 40 deg. The sun altitude is -35.3 deg.
The galactic latitude b = 60 deg., longitude l = 256 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2887934
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________
1789 | 2025-05-31 18:31:43 | MASTER-SAAO | (11h 22m 12.13s , +04d 56m 45.8s) | C | 60 | 19.5 | 1789 | 2025-05-31 18:31:43 | MASTER- | (11h 20m 21.93s , +05d 14m 38.0s) | C | 60 | 18.2 | 2577 | 2025-05-31 18:44:51 | MASTER-SAAO | (11h 30m 08.86s , +04d 56m 11.0s) | C | 60 | 19.3 | 2577 | 2025-05-31 18:44:51 | MASTER- | (11h 28m 19.20s , +05d 14m 00.4s) | C | 60 | 18.0 | 3202 | 2025-05-31 18:55:16 | MASTER-SAAO | (11h 22m 07.05s , +04d 58m 37.2s) | C | 60 | 19.5 | 3202 | 2025-05-31 18:55:16 | MASTER- | (11h 20m 17.21s , +05d 16m 27.2s) | C | 60 | 18.1 | 3797 | 2025-05-31 19:05:11 | MASTER-SAAO | (11h 30m 09.65s , +04d 57m 47.3s) | C | 60 | 19.3 | 3797 | 2025-05-31 19:05:11 | MASTER- | (11h 28m 19.98s , +05d 15m 38.0s) | C | 60 | 18.1 | 4208 | 2025-05-31 19:12:03 | MASTER-SAAO | (11h 22m 12.67s , +04d 57m 20.7s) | C | 60 | 19.4 | 4208 | 2025-05-31 19:12:03 | MASTER- | (11h 20m 22.82s , +05d 15m 08.3s) | C | 60 | 18.1 | 4404 | 2025-05-31 19:15:18 | MASTER-SAAO | (11h 30m 12.61s , +04d 57m 31.8s) | C | 60 | 19.3 | 4404 | 2025-05-31 19:15:18 | MASTER- | (11h 28m 22.60s , +05d 15m 21.9s) | C | 60 | 18.1 | 4501 | 2025-05-31 19:16:55 | MASTER-SAAO | (11h 20m 30.68s , +03d 04m 26.2s) | C | 60 | 19.4 | 4501 | 2025-05-31 19:16:55 | MASTER- | (11h 18m 41.05s , +03d 22m 16.5s) | C | 60 | 18.2 | 4594 | 2025-05-31 19:18:28 | MASTER-SAAO | (11h 28m 31.94s , +03d 05m 15.3s) | C | 60 | 19.4 | 4594 | 2025-05-31 19:18:28 | MASTER- | (11h 26m 42.18s , +03d 23m 06.9s) | C | 60 | 18.2 | 4688 | 2025-05-31 19:20:02 | MASTER-SAAO | (11h 24m 27.91s , +06d 51m 33.1s) | C | 60 | 19.4 | 4688 | 2025-05-31 19:20:02 | MASTER- | (11h 22m 37.83s , +07d 09m 23.1s) | C | 60 | 17.9 | 4783 | 2025-05-31 19:21:37 | MASTER-SAAO | (11h 32m 38.83s , +06d 51m 42.0s) | C | 60 | 19.2 | 4783 | 2025-05-31 19:21:37 | MASTER- | (11h 30m 48.71s , +07d 09m 32.8s) | C | 60 | 17.9 | 4877 | 2025-05-31 19:23:11 | MASTER-SAAO | (11h 22m 08.08s , +04d 59m 13.6s) | C | 60 | 19.5 | 4877 | 2025-05-31 19:23:11 | MASTER- | (11h 20m 18.35s , +05d 17m 04.3s) | C | 60 | 18.4 | Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
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