TITLE:   GCN CIRCULAR
NUMBER:  39323
SUBJECT: EP250207b: Xinglong optical upper limit
DATE:    25/02/14 10:19:21 GMT
FROM:    Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>

Junjie-Jin(NAOC), Haiyang-Mu(NAOC), Yue-Sun(NAOC), Zhou-Fan(NAOC),  Hong-Wu(NAOC) report on behalf of a large collaboration:
Following the detection of EP250207b by EP-WXT (Zhou et al., GCN 39266
), we observed the field of  EP250207b using Tsinghua-NAOC 0.8-m telescope (TNT) located at Xinglong, Hebei, China. A total of 3600 s N-band exposures were taken , with a median observation time of 2025-02-08T16:39:35, approximately 18.86 hours after the EP FXT trigger (2025-02-07T21:47:56). No optical counterpart was detected, with a 5-sigma limiting magnitude of 19.9, calibrated with Pan-STARRS sources in the field.