TITLE:   GCN CIRCULAR
NUMBER:  44230
SUBJECT: EP260402a/GRB 260402A: Xinglong optical upper limit
DATE:    26/04/07 15:05:38 GMT
FROM:    Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>

Min-He (NAOC),  Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Junjun-Jia (NAOC), Yuguang-Sun (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration:

Following the detection of EP260402a (Zhao et al., GCN 44186), we observed the field of EP260402a using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x300s clear-band frames by using 2.16-m with a median time of 2026-04-07T13:19:08, 5 days after the EP trigger.

No uncatalogued optical transient is detected in the stacked images within the 10 arcsec EP/FXT error circle (Zhao et al., GCN 44186), down to 3-sigma limiting magnitudes of Clear-band ~22.13 mag for for 2.16-m, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle.