EP J012607.7+121047: Einstein Probe detection of an X-ray transient associated with the candidate CV AT2023row/Gaia23cer
ATel #17525; W. J. Zhang (NAO, CAS), H. C. Ding, T. Wu (AHNU), Y. H. Jiang, Y. Wu (NJU), Y. Wang (PMO), Y. Liu (NAO, CAS), on behalf of the Einstein Probe (EP) team:
on 4 Dec 2025; 09:00 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: X-ray, Cataclysmic Variable, Nova
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP J012607.7+121047. The source was identified by stacking the WXT data spanning September 2025 to November 2025. Stacking of the WXT data taken prior to this detection indicated that the source had already emerged in August 2024. The WXT position of the source is R.A. = 21.510 deg, Dec. = 12.186 deg (J2000) with an uncertainty of 2.5 arcmin in radius (90% C.L. statistical and systematic). The estimated 0.5-4 keV flux derived from the WXT spectrum is ~3.5 x 10^(-12) erg/s/cm^2.
We performed a target-of-opportunity follow-up observation with the Follow-up X-ray Telescope (FXT) at 2025-12-02T15:20:59 (UTC). Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 21.5321 deg, Dec. = 12.1796 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The FXT position is around 3 arcsec away from the candidate CV AT2023row/Gaia23cer (Atel #16240 and #16249). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law, with a fixed Galactic hydrogen column density of 3.8 x 10^20 cm^-2 and a photon index of 1.14 (-0.09/+0.09). The derived average unabsorbed 0.5-10 keV flux is 2.18 (-0.21/+0.23) x 10^(-11) erg/s/cm^2.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
