TITLE: GCN CIRCULAR NUMBER: 45860 SUBJECT: The EP-WXT trigger 01709321008/EP261007b：Xinglong optical upper limit DATE: 26/10/08 13:46:42 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) Junbo-Zhang (NAOC), Junjie-Jin (NAOC), Rui-Zhu (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Yuguang-Sun (NAOC), Jie-Zheng (NAOC), Dong-Xu (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration Following the detection of EP261007b by EP-WXT (Wen et al., GCN 45847), we observed the field of EP261007b using the 0.8‑m and 2.16‑m telescopes at Xinglong Observatory, NAOC. We obtained 3 x 300 s g‑band frames with the 0.8‑m telescope at a median time of 2026‑10‑07T15:32:59 UTC, i.e., 0.46 hr after the EP trigger. The stacked g-band image has a 5-sigma limiting magnitude of ~20.66 mag, calibrated with the Pan-STARRS g-band field. For the 2.16‑m telescope, we obtained 3 x 300 s clear‑band frames with a median time of 2026‑10‑07T15:33:09 UTC, i.e., 0.46 hr after the EP trigger. The stacked clear-band image using the 2.16-m telescope has a 5-sigma limiting magnitude of ~22.21 mag, calibrated with the Pan-STARRS g-band field. No optical counterpart candidate was detected in our 0.8‑m and 2.16‑m observations. We summarize our observation results as follows: Obs. No. | Start Time (UTC) | End Time (UTC) |Exposure Time (s)|Upper limit mag| Telescope 1 | 2026-10-07 15:27:53 | 2026-10-07 15:43:05 | 3x300 s | 20.66 | Xinglong 0.8-m Telescope 2 | 2026-10-07 15:28:02 | 2026-10-07 15:43:41 | 3x300 s | 22.21 | Xinglong 2.16-m Telescope