TITLE: GCN CIRCULAR NUMBER: 42282 SUBJECT: GRB 251011B: SVOM/VT optical upper limit DATE: 25/10/15 07:42:44 GMT FROM: Yinuo Ma <mayn@bao.ac.cn> Y. N. Ma, H. L. Li, Z. H. Yao, L. P. Xin, 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, D. H. Zhao (NAOC), J. Palmerio (CEA), Y. H. Cheng (YNU), Y. Wang (PMO) report on behalf of the SVOM/VT team. SVOM performed a Target of Opportunity observation of GRB 251011B detected by Swift/BAT, Fermi/GBM, and SVOM/GRM (D'Ai et al., GCN 42197; Fermi GBM team, GCN 42196; Evans et al., GCN 42201; Mukherjee et al., GCN 42204; Sbarufatti et al., GCN 42205; Zao et al., GCN 42206). SVOM/VT began observing the field at 2025-10-11 09:06:00 UTC, 1.961 hours after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No uncatalogued sources, compared to Legacy Survey, were detected in our single or stacked images within the error box provided by Swift/XRT position (D'Ai et al., GCN 42197; Evans et al., GCN 42201), the three sigma limits are: mid-time | exposure time | band | upper limit (AB) ----------|-----------------|-------|----------------- 2.3 h | 44*50 sec | VT_B | > 23.2 mag 2.3 h | 41*50 sec | VT_R | > 23.3 mag Our results are consistent with MASTER (Balanutsa et al., GCN 42203) and Swift/UVOT (Siegel & D'Ai, GCN 42209). 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/42282. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...