TITLE: GCN CIRCULAR NUMBER: 44497 SUBJECT: EP260507a: SVOM/VT optical observations DATE: 26/05/08 03:08:14 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed observations with automatic follow-up observations to the Xray transient EP260507a triggered by Einstein Probe (Fu et al., GCN 44488). The observation started at 2026-05-07T14:45:27 UTC, i.e. 57.5 minutes post trigger and lasted for 2 orbits (about 1.9 hours) in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical counterpart (Corcoran et al., GCN 44489; Sankar et al., GCN 44490; Jiang et al., GCN 44491; Kumar et al., GCN 44492; Eyles-Ferris et al., GCN 44495; Jiang et al., GCN 44496) was clearly detected in both channels. The measurements in AB magnitude are as follows: Mid time | Band | Exposure Time | Brightness 1.35 h VT_B 56*50 s 21.92 +/- 0.12 mag 1.35 h VT_R 55*50 s 20.91 +/- 0.08 mag 2.96 h VT_B 56*50 s 22.29 +/- 0.14 mag 2.96 h VT_R 55*50 s 21.25 +/- 0.10 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/44497. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...