Einstein Probe detects fast X-ray transient EP260214b at z=1.208 with multi-wavelength follow-up

AI Summary

The Einstein Probe WXT detected a fast X-ray transient (EP260214b) on 2026-02-14 at RA=191.26°, DEC=23.857° with a 50-second duration and 0.5-4 keV flux of 2.1×10⁻⁹ erg/s/cm². The optical counterpart was rapidly identified and spectroscopically confirmed at redshift z=1.208 using VLT/X-shooter. Extensive multi-wavelength follow-up revealed optical fading from r'~20.9 mag at ~2.2 hours to r>22.2 mag by ~50 hours post-trigger, with radio non-detection at 17 days (3σ limit ~50 μJy) followed by detection at 34 days (~0.04 mJy), indicating delayed radio emission consistent with a relativistic outflow.