GCN Circular 46087
Subject
EP261010a: Xinglong optical follow-up
Event
Date
2026-10-29T09:39:53Z (3 days ago)
From
Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>
Via
Web form
Junjie-Jin (NAOC), Rui-Zhu (NAOC), Sen-Liu (NAOC), Haiyang-Mu (NAOC), Yu-Zhang (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration:
We observed the field of the X-ray transient EP261010a with the Beijing-Faint Object Spectrograph and Camera (BFOSC) on the Xinglong 2.16-m telescope on 2026 October 10. We obtained three 300-s exposures in the clear C band, for a total exposure time of 900 s. The midpoint of the observations was 2026-10-10 16:05:34.766 UTC.
No optical counterpart was identified within the 20-arcsec-radius EP/FXT error region. Image-subtraction photometry at the FXT localization yielded no significant detection. The representative 5-sigma point-source limiting magnitude measured from blank-sky apertures on the observed stack is 20.13 mag in the clear band, calibrated using PS1-r as the reference band.
Other optical follow-up observations also reported non-detections in the EP/FXT error region. NOT reported 5-sigma limits of r > 23.9 and z > 21.5 mag (Zhu et al., GCN 45882), and SVOM/VT reported 3-sigma limits of VT_B > 23.4 and VT_R > 23.1 mag (Ma et al., GCN 45884).