GCN Circular 39387

Y. L. Wang (NAOC, CAS), D. F. Hu (PMO, CAS), B. B. Zhang (BNU), P. Y. Han, C. X. Zhang (HUST), Y. Liu (NAOC, CAS) report on behalf of the Einstein Probe team:
 
We report on the detection of a fast X-ray transient by EP-WXT, designated EP250220a. The WXT position of the source is R.A. = 113.400 deg, DEC = 39.795 deg (J2000) with an uncertainty of 2.81 arcmin in radius (90% C.L. statistical and systematic). The flare starts from 2025-02-20T02:11:59 (UTC), lasting for about 150 seconds. The average 0.5-4 keV spectrum can be fitted with an absorbed powerlaw model, with NH fixed at the Galactic value of 7.13 x 10^20 cm^-2 and a photon index of 1.8 (-0.9/+1.0). The unabsorbed average 0.5-4 keV flux is estimated to be 5.8 (-2.2/+3.3) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.

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).