TITLE: GCN CIRCULAR NUMBER: 42896 SUBJECT: GRB 251126A: SAO RAS optical observations DATE: 25/11/29 17:15:20 GMT FROM: Alexander Moskvitin at SAO RAS <mosk@sao.ru> V. Goranskij (SAI MSU, SAO RAS), A. Moskvitin (SAO RAS), V. Shergin (SAO RAS), A. Volnova (IKI), N. Pankov (HSE, IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN and GRB follow-up team. We observed the field of the Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851; Page et al., GCN 42860; Barthelmy et al., GCN 42876) with the Zeiss-1000 1m telescope of the SAO RAS on November 28/29 night. We obtained a series of 300 and 600 sec. images in Rc band under a good weather conditions and FWHM of about 1".8. The optical afterglow (Swain, GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Anguloet al., GCN 42855; Pulido-Torres et al; GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859; Volnova et al., GCN 42861; Breeveld and Caputo, GCN 42863; Gupta et al., GCN 42864; Burkhonov et al., GCN 42866; Maksut et al., GCN 42868; Moskvitin et al, GCN 42870; Adami et al., GCN 42871; Pankov et al., GCN 42875) is clearly detected in the stacked frame. We report preliminary brightness of the optical afterglow. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-11-28 22:35:56 2.2236 8*300+4*600 Rc 23.15 0.18 23.7 The photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes)and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42896. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...