TITLE: GCN CIRCULAR NUMBER: 42941 SUBJECT: GRB 251126A: SVOM/VT optical observation DATE: 25/12/02 06:57:14 GMT FROM: zhyao@bao.ac.cn Z. H. Yao, Y. L. Qiu, C. Wu, H. L. Li, Y. N. Ma, L. P. Xin, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC) and J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 251126A detected by Swift/BAT (Caputo et al., GCN 42843). SVOM/VT began observing the field at 2025-11-26T19:45:56.502 UTC, 35 minutes after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Swain et al., GCN 42844; Lipunov et al. GCN 42847; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Angulo et 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 et al. 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; Goranskij et al. GCN 42896) was detected in both VT_B and VT_R band within BAT (Caputo et al., GCN 42843; Barthelmy et al. GCN 42876) and XRT's (Caputo et al., GCN 42843; Evans et al., GCN 42845; Goad et al., GCN 42851) error box. We detect a clear fading with a decay slope of approximately 1.6, followed by a rebrightening bump occurring at ~13.48 h after the trigger. The most recent photometric measurement is as follows: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|---------------- 25.34 | 20*70 | VT_B | 22.87+/-0.12 25.34 | 20*70 | VT_R | 21.64+/-0.05 Our photometry was not corrected for Galactic extinction. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42941. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...