TITLE: GCN CIRCULAR NUMBER: 40201 SUBJECT: Fermi GRB 250421A: Global MASTER-Net observations report DATE: 25/04/22 06:17:02 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250421A ( Fermi GBM team, GCN 40191) errorbox 67295 sec after notice time and 67337 sec after trigger time at 2025-04-22 05:20:48 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 33 deg. The sun altitude is -68.2 deg. The galactic latitude b = -9 deg., longitude l = 328 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2848837 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 67368 | 2025-04-22 05:20:48 | MASTER-OAFA | (16h 29m 49.10s , -59d 22m 10.8s) | C | 60 | 18.4 | 67601 | 2025-04-22 05:24:42 | MASTER-OAFA | (16h 25m 54.95s , -61d 15m 16.6s) | C | 60 | 18.4 | 67790 | 2025-04-22 05:28:01 | MASTER-OAFA | (16h 37m 54.84s , -62d 00m 16.5s) | C | 40 | 17.4 | 67800 | 2025-04-22 05:28:01 | MASTER-OAFA | (16h 57m 07.49s , -61d 33m 46.3s) | C | 60 | 18.9 | 68001 | 2025-04-22 05:31:22 | MASTER-OAFA | (16h 29m 45.37s , -59d 21m 53.7s) | C | 60 | 18.3 | 68194 | 2025-04-22 05:34:44 | MASTER-OAFA | (16h 41m 10.93s , -60d 04m 07.5s) | C | 40 | 17.2 | 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/40201. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...