TITLE: GCN CIRCULAR NUMBER: 39935 SUBJECT: GRB 250329B: SVOM/C-GFT optical upper limit DATE: 25/03/29 23:27:41 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> Chao WU (NAOC), W.J. Xie (NAOC), Y.H. Cheng (SWIFAR, YNU), B.T. Wang (YNAO, CAS), 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), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 250329B detected by SVOM/ECLAIRs (sb25032902) with C-GFT. Our observations were started on 2025-03-29T12:50:31 UTC, ~40.20 mins after the trigger. No any source was detected in our stacked image within the source error circle of the X-ray Swift/XRT (source #1: https://www.swift.ac.uk/SVOM/SVOM_FIELD00008/ ). The limiting magnitude(3 sigma) in i band is 19.80 mag at the middle time of 41.95 minutes after the burst. The photometry was calibrated with UCAC4 catalog. This result is consistent with the reports (Xin et al., GCN 39926, Chen et al., GCN 39929, and Xin et al., GCN 39931). We thank the observation assistants Yinhuai Hao and Bowen Li at Jilin observatory for their excellent support. Chinese Ground Follow-up Telescope of SVOM mission is located at Jilin, Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope. View this GCN Circular online at https://gcn.nasa.gov/circulars/39935. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...