TITLE: GCN CIRCULAR NUMBER: 42882 SUBJECT: GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data DATE: 25/11/29 04:12:26 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> C. Wu, H. L. Li, L.P. Xin, Y. L. Qiu (NAOC), J. T. Palmerio (CEA), W. J. Tan (IHEP), D. F. Kong (GXU) report on behalf of the SVOM team. After the trigger by SVOM/ECLAIRs at 2025-11-29T02:32:05 UTC (T0), SVOM/VT performed an automatic slew to the burst GRB 251129A (sb25112901, Tan et al., GCN 42879). The observation began at 2025-11-29T02:43:03, 658 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart reported (Angulo et al., GCN 42880) was clearly detected in the 1-bit subimages and source lists downloaded via VHF network in both channels. The magnitudes are : Mid_time Band Magnitude (AB) 808 sec VT_B 18.63+/-0.01 mag 808 sec VT_R 18.02+/-0.01 mag Our photometry was derived in AB magnitude and not corrected for Galactic extinction. Given the VT color, it is likely a low redshift GRB. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/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/42882. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...