TITLE: GCN CIRCULAR NUMBER: 42793 SUBJECT: EP251118a: Xinglong-2.16m optical observation DATE: 25/11/22 01:34:51 GMT FROM: liuxing@nao.cas.cn X. Liu, J.J. Jin, J. Zheng, Z. Fan, D. Xu, L.B. He, J. An, S.Q. Jiang, Z.P. Zhu, J.J. Jia(NAOC), S.Y. Fu(HUST) report on behalf of a large collaboration: We observed the field of EP251118a detected by EP/WXT (Jiang et al., GCN 42749; Shi et al., GCN 42754;) and likely GRB 251118C (Frederiks et al., GCN 42765; Wang et al., GCN 42766; Delaunay et al., GCN 42770; Woolf et al, GCN 42771) using the Xinglong-2.16m telescope equipped with the BFOSC camera. Observations started at 19:28:32 UT on 2025-11-21 (i.e., 74.77 h after the EP trigger), and 15x300 s R-band frames have been obtained. The optical afterglow (Melasani et al., GCN 42751; An et al., GCN 42756; Belkin et al., GCN42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Rodríguez et al., GCN 42773; Li et al., GCN 42776; Lee et al., GCN 42780; Moskvitin et al., GCN 42785; Gupta et al., GCN42787) was cleary detected in our stacked frame with a magnitude of R = 22.1 +/- 0.1 at a mid-time of 75.28hr, calibrated with Pan-STARRS1 DR2 catalog converted using Lupton (2005) equations and not corrected for Galactic extinction. We thank the staff at Xinglong observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42793. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...