TITLE: GCN CIRCULAR NUMBER: 37871 SUBJECT: GRB 241025A : SVOM/VT optical afterglow observations DATE: 24/10/25 09:59:39 GMT FROM: Liping Xin at NAOC, SVOM SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, C. Wu, L. P. Xin, X. H. Han, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM), H. Zhou (PMO), S. L. Xiong(IHEP) SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Olivier Godet (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV) report on behalf of the SVOM team: VT started to observe the field of GRB 241025A (Ambrosi et al., GCN#37859; Fermi GBM team, GCN#37860; Wang et al., GCN#37863; Li et al., GCN 37864)via ToO observations started at 2024-10-25T04:03:55 UT, about 2.45 hours after the burst. The VT conducted observations simultaneously in two channels: VT_B (400nm-650nm) and VT_R (650nm-1000nm). The counterpart (Ambrosi et al., GCN#37859; Jiang et al., GCN#37862, Pereyra et al., GCN#37865; Xu et al., GCN#37866) was clearly detected in both bands with VT_B=20.8+/-0.2 mag and VT_R=19.07+/-0.07 mag at 2.45 hours post the burst. More observations are on-going. 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.