TITLE: GCN CIRCULAR NUMBER: 43265 SUBJECT: GRB 251230A / EP251230a: SVOM/VT optical observation DATE: 25/12/30 09:58:05 GMT FROM: Yinuo Ma <mayn@bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), J. X. Cao (GXU), W. L. Zhang (PMO) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 251230A / EP251230a detected by Swift/BAT and EP/WXT (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263). SVOM/VT began observing the field at 2025-12-30T03:13:20 UTC, 1.861 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262) was clearly detected in both VT_B and VT_R bands. The magnitudes are: mid time (s) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|------|----------|-------- 6874 | 50 | VT_B | 19.11 | 0.04 8174 | 50 | VT_B | 19.53 | 0.05 6874 | 50 | VT_R | 18.57 | 0.03 8174 | 50 | VT_R | 19.07 | 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/43265. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...