TITLE:   GCN CIRCULAR
NUMBER:  46121
SUBJECT: EP261030a: Einstein Probe detection of a fast X-ray transient
DATE:    26/10/31 11:29:56 GMT
FROM:    EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

H.-H. Zhang, C.-Y. Dai (NJU), Y.-L. Wang (ICE, CSIC) and Y. Liu (NAOC) on behalf of the Einstein Probe (EP) team:

We report on the detection of a fast X-ray transient, designated EP261030a, identified in the downlinked data from the Wide-field X-ray Telescope (WXT) aboard the Einstein Probe (EP) mission. The WXT light curve of the transient began at about 2026-10-30T17:15:19 UTC and lasted for about 100 s. The WXT position of the source is R.A. = 23.663 deg, DEC = -11.691 deg (J2000) with an uncertainty of 3.2 arcmin in radius (90% C.L. statistical and systematic).

The 0.5-4 keV WXT spectrum can be fitted by an absorbed power-law model with a fixed Galactic column density of 2.4 x 10^20 cm^-2 and a photon index of 1.0 (-0.4,+0.4). The derived 0.5-4 keV unabsorbed flux is 3.6 (-0.9/+1.1) x 10^-10 erg/cm^2/s.

A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP has been scheduled. Further information will be updated when the telemetry data is received.

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).