TITLE: GCN CIRCULAR NUMBER: 41994 SUBJECT: Fermi GRB 250926A: Global MASTER-Net observations report DATE: 25/09/26 01:31:05 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 250926A ( Fermi GBM team, GCN 41993) errorbox 71 sec after notice time and 114 sec after trigger time at 2025-09-26 00:23:18 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 53 deg. The sun altitude is -47.4 deg. The galactic latitude b = -20 deg., longitude l = 210 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3000001 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 124 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 28m 42.38s , -08d 02m 54.5s) | C | 20 | 18.4 | 159 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 28m 42.37s , -08d 02m 54.4s) | C | 90 | 19.4 | Coadd 124 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 30m 34.49s , -08d 18m 14.3s) | C | 20 | 18.4 | 159 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 30m 34.49s , -08d 18m 14.2s) | C | 90 | 19.5 | Coadd 168 | 2025-09-26 00:23:57 | MASTER-SAAO | (05h 28m 42.29s , -08d 02m 53.3s) | C | 30 | 18.6 | 168 | 2025-09-26 00:23:57 | MASTER-SAAO | (05h 30m 34.43s , -08d 18m 12.4s) | C | 30 | 18.7 | 222 | 2025-09-26 00:24:46 | MASTER-SAAO | (05h 28m 42.23s , -08d 02m 51.9s) | C | 40 | 18.8 | 222 | 2025-09-26 00:24:46 | MASTER-SAAO | (05h 30m 34.40s , -08d 18m 10.2s) | C | 40 | 18.8 | 286 | 2025-09-26 00:25:45 | MASTER-SAAO | (05h 28m 42.20s , -08d 02m 50.5s) | C | 50 | 18.9 | 286 | 2025-09-26 00:25:45 | MASTER-SAAO | (05h 30m 34.36s , -08d 18m 08.0s) | C | 50 | 19.0 | 360 | 2025-09-26 00:26:54 | MASTER-SAAO | (05h 28m 42.14s , -08d 02m 49.6s) | C | 60 | 19.1 | 360 | 2025-09-26 00:26:54 | MASTER-SAAO | (05h 30m 34.29s , -08d 18m 06.4s) | C | 60 | 19.2 | 651 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 28m 05.28s , -07d 01m 44.0s) | C | 60 | 18.7 | 711 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 28m 05.28s , -07d 01m 44.0s) | C | 180 | 19.4 | Coadd 651 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 29m 57.17s , -07d 16m 59.6s) | C | 60 | 18.8 | 711 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 29m 57.17s , -07d 16m 59.6s) | C | 180 | 19.5 | Coadd 731 | 2025-09-26 00:33:04 | MASTER-SAAO | (05h 28m 05.23s , -07d 01m 43.2s) | C | 60 | 18.7 | 731 | 2025-09-26 00:33:04 | MASTER-SAAO | (05h 29m 57.12s , -07d 16m 58.5s) | C | 60 | 18.8 | 810 | 2025-09-26 00:34:23 | MASTER-SAAO | (05h 28m 05.16s , -07d 01m 43.1s) | C | 60 | 18.7 | 810 | 2025-09-26 00:34:23 | MASTER-SAAO | (05h 29m 57.08s , -07d 16m 58.0s) | C | 60 | 18.8 | 890 | 2025-09-26 00:35:43 | MASTER-SAAO | (05h 28m 05.10s , -07d 01m 42.8s) | C | 60 | 18.6 | 890 | 2025-09-26 00:35:43 | MASTER-SAAO | (05h 29m 57.06s , -07d 16m 57.6s) | C | 60 | 18.8 | 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/41994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...