General information
EP260527a is a fast X-ray transient detected by Einstein Probe/WXT on 2026-05-27 06:19:54 UTC, with subsequent EP/FXT follow-up and a reported optical detection consistent with the FXT localization.
Wavelength coverage
- X-ray: EP-WXT detected a ~200 s transient; EP-FXT follow-up ~20.5 hr later found an uncatalogued X-ray source in the WXT error circle.
- Optical: COLIBRÍ/DDRAGO obtained g/r/z imaging ~21.9–23.8 hr post-trigger and detected an uncatalogued source within the FXT uncertainty region (g=22.25, r=22.19, z=21.52 AB).
No observations were mentioned in gamma-rays, UV, IR, radio, neutrinos, or gravitational waves.
Lightcurve and spectrum
- WXT transient start time reported as 2026-05-27 06:16:18 UTC with duration ~200 s.
- WXT 0.5–4.0 keV spectrum fit by an absorbed power law with photon index 0.73 (+0.44/-0.42), with Galactic NH fixed to 1.57×10^20 cm^-2.
- Unabsorbed 0.5–4.0 keV flux reported as 1.12 (+0.33/-0.28) × 10^(-9) erg s^-1 cm^-2.
- Optical stacked-image magnitudes: g=22.25±0.32, r=22.19±0.17, z=21.52±0.15 (AB; not corrected for Galactic extinction).
Redshift
What’s special vs typical
- A likely counterpart is reported in both X-rays (FXT) and optical (COLIBRÍ) at consistent positions within the FXT uncertainty region, increasing interest beyond a single-instrument trigger.
- The optical detection in g is explicitly noted as suggesting the event is not high-redshift.