TITLE: GCN CIRCULAR NUMBER: 39952 SUBJECT: Fermi GRB 250330B: Global MASTER-Net observations report DATE: 25/03/30 23:15:59 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) started inspect of the Fermi GRB 250330B ( Fermi GBM team, GCN 39951) errorbox 54 sec after notice time and 92 sec after trigger time at 2025-03-30 21:53:54 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 77 deg. The sun altitude is -59.7 deg.

The galactic latitude b = 16 deg., longitude l = 206 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2828695

We obtain a following upper limits.

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

102 | 2025-03-30 21:53:54 | MASTER-SAAO | (07h 22m 19.10s , +12d 01m 03.3s) | C | 20 | 17.1 | 141 | 2025-03-30 21:54:33 | MASTER-SAAO | (07h 22m 19.82s , +12d 01m 05.9s) | C | 20 | 17.0 | 186 | 2025-03-30 21:55:12 | MASTER-SAAO | (07h 22m 20.65s , +12d 01m 08.5s) | C | 30 | 17.1 | 240 | 2025-03-30 21:56:01 | MASTER-SAAO | (07h 22m 21.73s , +12d 01m 11.2s) | C | 40 | 17.0 | 304 | 2025-03-30 21:57:00 | MASTER-SAAO | (07h 22m 23.03s , +12d 01m 14.3s) | C | 50 | 16.9 | 378 | 2025-03-30 21:58:10 | MASTER-SAAO | (07h 22m 24.54s , +12d 01m 18.1s) | C | 60 | 16.9 | 629 | 2025-03-30 22:02:21 | MASTER-SAAO | (07h 36m 00.30s , +13d 19m 14.0s) | C | 60 | 17.4 | 709 | 2025-03-30 22:03:40 | MASTER-SAAO | (07h 36m 01.77s , +13d 19m 17.5s) | C | 60 | 17.4 | 788 | 2025-03-30 22:04:59 | MASTER-SAAO | (07h 36m 03.30s , +13d 19m 20.6s) | C | 60 | 17.4 | Filter C is a clear (unfiltred) band.

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

View this GCN Circular online at https://gcn.nasa.gov/circulars/39952. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...