TITLE: GCN CIRCULAR NUMBER: 42024 SUBJECT: GRB 250916A: SVOM/VT optical observation DATE: 25/09/29 01:39:36 GMT FROM: Liping Xin at NAOC, SVOM <xlp@nao.cas.cn> L. P. Xin, H. L. Li, Y. N. Ma, Z. H. Yao, Y. L. Qiu, C. Wu, 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), W. K. Zheng (UCT), Z. Q. Wang (GXU) report on behalf of the SVOM/VT team: SVOM/VT performed a Target of Opportunity observation of GRB 250916A detected by Fermi GBM team (GCN 41839), starting at 2025-09-23T07:32:29 UTC, 6.66 days after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (Belkin et al., GCN Circ. 41847; Mohan et al., GCN Circ. 41858; Moskvitin et al., GCN Circ. 41859; Burkhonov et al., GCN Circ. 41860; de Ugarte Postigo et al., GCN Circ. 41863; Moskvitin et al., GCN Circ. 41870; Zheng and Filippenko, GCN Circ. 41873; Pankov et al., GCN Circ. 41892; Hall et al., GCN Circ. 41921 and Moskvitin et al., GCN Circ. 41934, Breeveld et al., GCN 41938) was detected in both channels. The brightness was VT_R=23.0 +/-0.25 mag, VT_B=23.5+/-0.3 mag, with an effective exposure time of 97*70 seconds. Our photometry was in AB magnitude and 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 Centre 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/42024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...