GCN Circular 38289

S. K. Yang (WHU), X. P. Xu, M. J. Liu (NAO, CAS), Q. C. Shui (IHEP, CAS), H. Z. Wu (HUST), H. He (WHU), Y. L. Hua (PMO, CAS), W. D. Zhang, W. Yuan (NAO, CAS) on behalf of the Einstein Probe team 

We report on the detection of an X-ray transient detected by EP-WXT, which triggered the on-board processing unit at 2024-11-20 18:10:01 (UTC) (trigger ID: 01709122294). The source position is R.A. = 64.628 deg, DEC = 28.458 deg (J2000) with an uncertainty of about 2.0 arcmin (radius, 90% C.L. statistical and systematic). An autonomous follow-up observation of the X-ray transient was performed by EP-FXT, which detected an X-ray source at R.A. = 64.6292 deg, DEC = 28.4548 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), consistent with the WXT position. V410 Tau, a K-type, Orion Variable star is about 1.7 arcsec away from the position determined by FXT and is therefore located within the FXT error circle. The distance to V410 Tau is 129 pc. We suggest that this X-ray transient is most likely a stellar flare event occurred on this star.

The WXT spectrum can be fitted with an absorbed apec model with a temperature of 3 (+5/-1) keV. The unabsorbed 0.5-4 keV flux of the WXT source is 3.7 (+1.3/-1.1) x 10^-11 erg/s/cm^2. If this transient is indeed associated with V410 Tau, its luminosity is around 7.3 x 10^31 erg/s in the 0.5-4 keV range. (The quoted errors of the parameters derived above are at the 90% C.L.). 

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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.