GCN Circular 45860

Subject

The EP-WXT trigger 01709321008/EP261007b：Xinglong optical upper limit

Event

Date

2026-10-08T13:46:42Z (12 hours ago)

From

Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>

Via

Web form

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 45847Loading...
 
 ), 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