TITLE: GCN CIRCULAR NUMBER: 42011 SUBJECT: Fermi trigger No 780609036: Global MASTER-Net observations report DATE: 25/09/26 20:30:38 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 GRB250926.83 (trigger No 780609036,19h 26m 38.40s , -80d 55m 48.0s, R=7.6) errorbox 112 sec after notice time and 144 sec after trigger time at 2025-09-26 19:52:55 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 54 deg. The sun altitude is -40.0 deg. The galactic latitude b = -29 deg., longitude l = 313 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3000539 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 160 | 2025-09-26 19:52:55 | MASTER-SAAO | (00h 31m 12.67s , -84d 57m 34.6s) | C | 30 | 16.7 | 205 | 2025-09-26 19:52:55 | MASTER-SAAO | (00h 31m 12.74s , -84d 57m 34.5s) | C | 120 | 17.8 | Coadd 160 | 2025-09-26 19:52:55 | MASTER-SAAO | (00h 52m 18.08s , -85d 11m 39.8s) | C | 30 | 17.1 | 205 | 2025-09-26 19:52:55 | MASTER-SAAO | (00h 52m 18.11s , -85d 11m 39.9s) | C | 120 | 18.2 | Coadd 214 | 2025-09-26 19:53:44 | MASTER-SAAO | (00h 31m 11.30s , -84d 57m 37.0s) | C | 40 | 17.0 | 214 | 2025-09-26 19:53:44 | MASTER-SAAO | (00h 52m 17.26s , -85d 11m 41.8s) | C | 40 | 17.4 | 278 | 2025-09-26 19:54:43 | MASTER-SAAO | (00h 31m 10.47s , -84d 57m 38.0s) | C | 50 | 17.4 | 278 | 2025-09-26 19:54:43 | MASTER-SAAO | (00h 52m 16.41s , -85d 11m 42.8s) | C | 50 | 17.8 | 352 | 2025-09-26 19:55:52 | MASTER-SAAO | (00h 31m 09.08s , -84d 57m 36.9s) | C | 60 | 17.1 | 352 | 2025-09-26 19:55:53 | MASTER-SAAO | (00h 52m 14.97s , -85d 11m 43.7s) | C | 60 | 17.6 | 1541 | 2025-09-26 20:15:41 | MASTER-SAAO | (19h 47m 45.38s , -84d 30m 55.3s) | C | 60 | 14.1 | 1541 | 2025-09-26 20:15:41 | MASTER-SAAO | (19h 29m 45.92s , -84d 14m 40.6s) | C | 60 | 15.1 | 1796 | 2025-09-26 20:19:57 | MASTER-SAAO | (16h 56m 37.37s , -84d 03m 27.9s) | 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/42011. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...