TITLE: GCN CIRCULAR NUMBER: 41484 SUBJECT: Fermi GRB 250821B: Global MASTER-Net observations report DATE: 25/08/22 02:45:40 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-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 250821B ( Fermi GBM team, GCN 41473) errorbox 26834 sec after notice time and 35938 sec after trigger time at 2025-08-22 02:06:45 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 63 deg. The sun altitude is -50.3 deg. The galactic latitude b = -39 deg., longitude l = 295 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2974796 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 35953 | 2025-08-22 02:06:45 | MASTER-OAFA | (02h 39m 51.65s , -77d 15m 11.6s) | C | 30 | 18.2 | 36003 | 2025-08-22 02:07:35 | MASTER-OAFA | (02h 39m 51.48s , -77d 14m 09.1s) | C | 30 | 18.2 | 36081 | 2025-08-22 02:08:38 | MASTER-OAFA | (02h 39m 55.46s , -77d 15m 05.3s) | C | 60 | 18.5 | 36162 | 2025-08-22 02:09:59 | MASTER-OAFA | (02h 39m 48.90s , -77d 16m 01.7s) | C | 60 | 18.4 | 36246 | 2025-08-22 02:11:23 | MASTER-OAFA | (02h 39m 55.59s , -77d 15m 36.4s) | C | 60 | 18.4 | 36370 | 2025-08-22 02:13:27 | MASTER-OAFA | (02h 39m 50.79s , -77d 14m 15.1s) | C | 60 | 18.6 | 36494 | 2025-08-22 02:15:31 | MASTER-OAFA | (02h 39m 49.56s , -77d 15m 45.5s) | C | 60 | 18.2 | 36592 | 2025-08-22 02:17:09 | MASTER-OAFA | (02h 39m 51.22s , -77d 13m 46.7s) | C | 60 | 18.7 | 36673 | 2025-08-22 02:18:30 | MASTER-OAFA | (02h 39m 44.40s , -77d 14m 42.5s) | C | 60 | 18.8 | 36749 | 2025-08-22 02:19:46 | MASTER-OAFA | (02h 39m 43.93s , -77d 13m 40.2s) | C | 60 | 18.5 | 36829 | 2025-08-22 02:21:06 | MASTER-OAFA | (02h 39m 50.13s , -77d 14m 36.9s) | C | 60 | 18.8 | 36918 | 2025-08-22 02:22:34 | MASTER-OAFA | (02h 39m 43.66s , -77d 15m 33.3s) | C | 60 | 17.7 | 37024 | 2025-08-22 02:24:21 | MASTER-OAFA | (02h 39m 46.86s , -77d 15m 02.4s) | C | 60 | 17.9 | 37132 | 2025-08-22 02:26:09 | MASTER-OAFA | (02h 39m 43.59s , -77d 13m 42.4s) | C | 60 | 17.9 | 37229 | 2025-08-22 02:27:46 | MASTER-OAFA | (02h 39m 42.71s , -77d 15m 06.5s) | C | 60 | 17.9 | 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/41484. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...