GCN 45215: EP260725a: EP-FXT follow-up observation and association with a bright flaring star

2026-07-26T08:11:38.838Z | rev 0 | event: EP260725a

R. D. Liang (NAOC), Y. J. Zhang (PKU), W. Chen, H. W. Pan (NAOC), on behalf of the Einstein Probe (EP) team

EP-FXT performed a follow-up observation of EP260725a, an X-ray transient detected by EP-WXT (GCN 45214), about 15 hrs after the WXT detection. 

The updated EP-FXT position is R.A. = 337.0689 deg and DEC = 50.7748 deg (J2000), with an uncertainty radius of 10 arcsec (90% confidence level, including statistical and systematic uncertainties), which is consistent with the known RS CVn-type variable star ZTF J222816.62+504629.8. The averaged unabsorbed flux in 0.5-10 keV is about 1.2 x 10^(-12) erg/cm^2/s. The corresponding EP-WXT X-ray luminosity is estimated to be approximately 1.1x 10^34 erg/s.

Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic soft X-ray sky with rapid X-ray follow-up capability (Yuan et al. 2022; Handbook of X-ray and Gamma-ray Astrophysics).