GCN Circular 45153

X. H. Tang (THU), M. J. Liu (NAO, CAS), Y. L. Hua (PMO, CAS), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team:

We report on the detection of an X-ray transient designated EP260713a by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient was detected at 2026-07-13T15:25:54 (UTC) at R.A. = 283.210 deg, DEC = -13.129 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). Preliminary analysis shows that the WXT spectrum can be fitted by an absorbed blackbody spectrum with NH = 0.8(-0.7/+1.8)e22 cm-2 and a temperature of 0.12(-0.07/+0.21) keV. The derived 0.5-4 keV flux is 6.9(-1.2/+2.9)e-12 erg/s/cm^2. The uncertainties are given at the 90% confidence level for the above parameters.

An observation on this X-ray transient was performed by the Follow-up X-ray Telescope (FXT) on board EP at 2026-07-14T07:01:57 (UTC), which detected an uncatalogued X-ray source at R.A. = 283.2049, DEC = -13.1132 deg (J2000, with an uncertainty of about 20 arcsec), consistent with the position of the WXT transient within the uncertainties. Further information will be updated when the telemetry data are 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).