GCN Circular 37902

T.Y. Lian, D. Y. Li, Y. L. Wang, S. X. Wen. W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team:

We report on the detection of a fast X-ray transient, designated EP241026b, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2024-10-26T18:14:30(UTC) and lasted for around 100 seconds. The WXT position of EP241026b is R.A.= 56.403 deg, DEC = 41.031 deg (J2000) with an uncertainty of 2.9 arcmin (radius, 90% C.L. statistical and systematic).  It has a peak flux of ~1.7 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 2.5(+/-0.8) (with a column density fixed at the Galactic value of 3.38 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 1.2(-0.3, +0.4) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 

No previously known bright X-ray sources are found within the error circle around the source position. EP-FXT follow-up observation has been arranged. Further follow-up observations are encouraged to identify the nature of this X-ray transient. 

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).