GCN Circular 43729

J. Yang (ZZU), R.-Z. Li (YNAO, CAS), X. Tian (GXU), W. D. Zhang (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 EP260213a. The transient triggered EP-WXT (ID: 01709258378) at 2026-02-13T19:58:40 (UTC). The WXT position of the source is R.A. = 167.008 deg, DEC = 3.965 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=2026-02-13T19:58:00 (UTC), and lasted for approximately 40 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 5.60 × 10^20 cm^-2 and a photon index of 0.6 (+/-0.6). The derived average unabsorbed 0.5-4 keV flux is 1.4 (-0.4/+0.5) × 10^(-9) erg/s/cm^2.

A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 167.0083 deg, DEC = 3.9451 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).

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).