TITLE: GCN CIRCULAR NUMBER: 42577 SUBJECT: GRB 251103A: WFST optical observations DATE: 25/11/04 13:13:47 GMT FROM: ylhua@pmo.ac.cn Yan-Long Hua, Chao Wu (NAOC), Jin-Jun Geng, Xue-Feng Wu, Jun-Jie Wei, Tian-Rui Sun, Yi-Fang Liang, Ding-Fang Hu, Guan-Xiao Li, Yuan-Tai Yang, Jia-Zheng Zhu, Ze-Lin Xu, Ning Jiang, Ji-An Jiang report on behalf of the WFST team: Following the detection of GRB 251103A by SVOM(Hu et al., GCN 42534，Benjamin Schneider et al., GCN 42549,Chen-Wei Wang et al., GCN 42552), Fermi/GBM (Fermi GBM Team, GCN 42536, GCN 42553), Swift (J.P. Osborne et al., GCN 42551,A. A. Breeveld et al., GCN 42554). 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 in the r/g band began at 2025-11-03T20:57:29 UTC, approximately 16 hours after the trigger. The afterglow is detected in r/g band we measured the following preliminary magnitude: r = 20.82 +/- 0.16,2025-11-03T20:59:45 UTC g = 21.10 +/- 0.12,2025-11-03T22:30:38 UTC The photometric calibration was performed using nearby stars from the PanSTARRS catalog is in the AB system, and is not corrected for Galactic extinction. We thank the WFST staff for supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42577. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...