TITLE: GCN CIRCULAR NUMBER: 41684 SUBJECT: GRB 250903A: SVOM/VT optical confirmation with VHF data DATE: 25/09/03 21:14:00 GMT FROM: Liping Xin at NAOC, SVOM <xlp@nao.cas.cn> L.P. Xin, H.L. Li, C. Wu. Y. L. Qiu, Z.H. Yao, Y.N. Ma, X.H. Han, J. Wang, W.J. Xie, Y. Xu, H.B. Cai, J. Y. Wei (NAOC), J. Palmerio (CEA), Tais Maiolino (LUPM), Claire Guépin-Detrigne (LUPM) report on behalf of the SVOM team. SVOM/VT performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Maiolino et al. GCN 41677). SVOM/VT began observing the field automatically at 2025-09-03T18:15:57 UTC, about 52 min after the T0, with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.   With downlinked VHF data, the optical counterpart reported (An et al., GCN 41679) within the errorbox of SVOM/MXT (GOTZ et al., GCN 41681) was clear detected with the brightness of VT_B=20.12+/-0.03 and VT_R=19.65 +/-0.03 mag at 54.5 min after the trigger. More follow-ups are encouraged.  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/41684. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...