GCN Circular 43744

J. Yang (ZZU), A. Li (BNU), Y. H. Jiang (NJU) and Y. Liu (NAOC) on behalf of the Einstein Probe (EP) team: 

We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260214b. The transient triggered EP-WXT (ID: 01709258389) at 2026-02-14T22:04:12 (UTC). The WXT position of the source is R.A. = 191.260 deg, DEC = 23.857 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The preliminary analysis of the WXT data shows that the event started at T0=2026-02-14T22:03:34 (UTC), and lasted for approximately 50 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.57 × 10^20 cm^-2 and a photon index of 0.7 (+/-0.4). The derived average unabsorbed 0.5-4 keV flux is 2.1 (-0.5/+0.7) × 10^(-9) erg/s/cm^2.

As the EP was performing another autonomous follow-up observation, no follow-up observation was performed automatically for this source. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed at 2026-02-15T03:59:57 (UTC), about 6 hours after T0. Within the WXT error circle, the FXT on-board alert indicated an uncatalogued X-ray source at R.A. = 191.2598 deg, DEC = 23.8533 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).

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).