TITLE: GCN CIRCULAR NUMBER: 41854 SUBJECT: GRB250917B: WFST optical observations DATE: 25/09/17 19:16:36 GMT FROM: ylhua@pmo.ac.cn Yan-Long Hua, Bin Li, Bin-Yang Liu, Tian-Rui Sun, Jin-Jun Geng, Xue-Feng Wu, Zhi-Ping Jin, Wen Zhao, Ji-An Jiang report on behalf of the WFST team: Following the detection of GRB 250917B by Fermi GBM (Fermi GBM Team, GCN 41846) and Swift-BAT (R. Caputo, GCN 41848), we performed follow-up observations using the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at the Lenghu Astronomical Observation Base in Qinghai Province, China. Observations were performed in the g/r/i band, starting from 2025-09-17 13:15:02（UTC）to 2025-09-17 13:42:39（UTC）, with an exposure of 120s*3 for each band. The r-band stacked image reaches a limiting magnitude of 22.3 (AB). We performed image subtraction using Pan-STARRS1 (PS1) reference images, but did not find any significant optical counterpart. We also examined the Swift-XRT (J.A. Kennea, GCN 41851) sources within the GRB error region: Source 1 is located near the center of a galaxy, making it difficult to justify an optical counterpart. Source 5 and Source 6 show no detectable optical counterparts in our images. These results suggest that no clear optical afterglow was detected at the positions of the X-ray sources within our observation limits. We thank the WFST staff for supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...