TITLE: GCN CIRCULAR NUMBER: 42767 SUBJECT: EP251118A / GRB 251118C : MASTER optical counterpart observations DATE: 25/11/19 17:40:22 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> Carlos Francile, Ricardo Podesta, Federico Podesta (OAFA), V. Lipunov, A.Kuznetsov, E.Gorbovskoy, G.Antipov, P.Balanutsa, I. Panchenko, N. Tiurina, K.Zhirkov, Ya.Kechin, A.Chasovnikov, V.Topolev, D. Vlasenko, Yu. Tselik, V.Senik (Lomonosov MSU, SAI, Moscow), E. Gonzalez (OAFA, San Juan Uni., Argentina), D. Buckley (SAAO, South Africa), O. Gress, N.Budnev, O.Ershova (Irkutsk State University), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez,A.R.Corella,L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) MASTER-OAFA robotic telescope (Global MASTER Net [1-4],http://observ.pereplet.ru) located in Argentina started EP251118A (EP:Jiang et al. GCN 42749, Shi et al. GCN 42754, Konus-Wind: Frederiks et al. GCN 42765 as GRB 251118C) at 2025-11-19 07:57:04 UT (Lipunov et al. GCN 42755) There is optical transient MASTER OT J081239.45+105619.7 with m_OT=19.8 at 2025-11-19 07:57:04UT (calibrated by Gaia G). This optical counterpart of GRB 251118C was discovered by NOT (Malesani et al. GCN 42751) and also observed by VLT (Yadav et al. GCN 42760) and FTW (Busmann et al. GCN 42763) MASTER observations started at 45 degrees altitude (Sun_alt=-17deg) View this GCN Circular online at https://gcn.nasa.gov/circulars/42767. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...