GCN Circular 40118

D. F. Hu, T. C. Zheng (PMO, CAS), X. Mao, W. X. Wang, W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team:

We report on the detection of a fast X-ray transient EP250407a detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2025-04-07T23:27:23 (UTC) and lasted for about 70s. We apologize that an incorrect trigger date was reported in the GCN Notice (trigger ID: 11916648441). The WXT position of EP250407a is R.A.= 134.813 deg, DEC = -38.956 deg (J2000) with an uncertainty of 2.5 arcmin (radius, 90% C.L. statistical and systematic). No known X-ray sources are found within the WXT error circle. The average 0.5-4 keV spectrum can be fitted with an absorbed powerlaw with a photon index of 1.4 (+/-0.6) and a fixed Galactic hydrogen column density of 4.67 x 10^21 cm^-2. We derive an average unabsorbed flux of 4.7(-1.0/+1.2) x 10^(-9) erg/s/cm^2, and a peak flux of approximately 1.0 x 10^(-8) erg/s/cm^2 (both in 0.5-4 keV).

A follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP is planned. Further follow-up observations are encouraged to identify the nature of this X-ray transient. 

The contact TA of this source is Ding-Fang Hu, please contact him via the email dfhu@pmo.ac.cn if needed.

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).