TITLE: GCN CIRCULAR NUMBER: 42776 SUBJECT: EP251118a / GRB 251118C: SVOM/VT optical observation DATE: 25/11/20 06:52:54 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, Y. Xu, X. H. Han, 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), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation on EP251118a/GRB 251116C (Jiang et al., GCN 42749; Shi et al., GCN 42754; Frederiks et al., GCN 42765; Wang et al., GCN 42766; Delaunay et al., GCN 42770; Woolf et al, GCN 42771). The observation started at 2025-11-19T07:02:19 UT, i.e. 14.33 hour after EP-WXT staring time in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart reported by Malesani et al. (GCN 42751) and other optical observations (An et al., GCN 42756; Belkin et al, GCN 42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Urquijo-Rodríguez et al., GCN 42773) was clearly detected by VT in both channels. The measurements in AB magnitudes were derived as below: Mid time | Band | Exposure Time | Magnitudes (AB) 15.84 hour VT_B 20*70 sec 21.07+/-0.05 mag 15.84 hour VT_R 20*70 sec 20.64+/-0.05 mag 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/42776. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...