TITLE: GCN CIRCULAR NUMBER: 45528 SUBJECT: Fermi GRB 260907B: Global MASTER-Net observations report DATE: 26/09/07 17:33:28 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs D.Buckley (SAAO), 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 (Lomonosov MSU) A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) A.Sosnovskij (CrAO RAS) A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) R.Rebolo (The Instituto de Astrofisica de Canarias) O.Gress, N.Budnev(ISU) M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260907B ( Fermi GBM team, GCN 45525) errorbox 33321 sec after notice time and 33352 sec after trigger time at 2026-09-07 17:11:16 UT, with upper limit up to 17.0 mag. Observations started at twilight. The observations began at zenith distance = 77 deg. The sun altitude is -11.2 deg. The galactic latitude b = -22 deg., longitude l = 79 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3500122 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 33383 | 2026-09-07 17:11:16 | MASTER-SAAO | (21h 29m 44.20s , +21d 44m 03.7s) | C | 60 | 16.4 | 33476 | 2026-09-07 17:12:49 | MASTER-SAAO | (21h 29m 50.74s , +21d 43m 05.9s) | C | 60 | 16.5 | 33570 | 2026-09-07 17:14:24 | MASTER-SAAO | (21h 38m 21.42s , +21d 41m 51.3s) | C | 60 | 16.3 | 33664 | 2026-09-07 17:15:57 | MASTER-SAAO | (21h 38m 27.60s , +21d 42m 08.7s) | C | 60 | 16.6 | 33761 | 2026-09-07 17:17:34 | MASTER-SAAO | (21h 29m 47.38s , +21d 42m 19.0s) | C | 60 | 17.0 | 33856 | 2026-09-07 17:19:09 | MASTER-SAAO | (21h 38m 27.46s , +21d 43m 52.6s) | C | 60 | 16.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html