EP251102b: Einstein Probe detection of an X-ray transient
ATel #17480; Y.-F. Liang, H. Zhou (PMOC) and H.-W. Pan (NAOC) on behalf of the Einstein Probe (EP) team:
on 6 Nov 2025; 09:08 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: X-ray, Transient
Referred to by ATel #: 17481
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 EP251102b. The source was detected by EP-WXT on 2025-11-02 at 00:16:10 (UTC). The WXT position of the source is R.A. = 89.821 deg, DEC = -71.681 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law. The derived average unabsorbed 0.5-4 keV flux is 3.0(-0.6/+0.7) x 10^(-11) erg/s/cm^2.
We performed a target-of-opportunity follow-up observation with the Follow-up X-ray Telescope (FXT) at 2025-11-04T17:46:12 (UTC). Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 89.8527 deg, DEC = -71.7069 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average unabsorbed 0.5-10 keV flux is 8.7 (-0.4/+0.4) x 10^(-12) erg/s/cm^2.
Further multi-wavelength observations are encouraged to determine the nature of this source.
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).
