TITLE: GCN CIRCULAR NUMBER: 40547 SUBJECT: EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation DATE: 25/05/24 07:03:12 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao (NAOC), Yulei, Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng (NAOC), Lei Huang (NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of the X-ray transient WXT trigger 01709176712 from the Einstein Probe (Yang et al., GCN 40537) with LATIOS on SVOM/C-GFT. Observations started at 2025-05-23T12:52:03, ~7.54 mins after the trigger. A series of g, r, and i-band images were obtained over ~2.58 hr. Preliminary analysis shows that the flare star reported by Yang et al. (GCN 40537) and Neill et al. (GCN 40542) exhibited a g-band magnitude decline from 11.36 mag to 12.95 mag, with a color variation (g−i) of~ 0.73 mag (from −0.24 to +0.49) between 11 and 162 minutes post trigger. Magnitudes were calibrated with nearby Pan-STARRS1 stars and were not corrected for dust extinction. We thank the observation assistants Bowen Li and Shuai Liu at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec ×21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k×4k CMOS camera at the prime focus with a 1.28 deg × 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/40547. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...