General information
EP260822a is a fast X-ray transient detected by Einstein Probe/WXT at 2026-08-22T15:16:02 UTC at RA 14.334 deg, Dec 11.275 deg, with a 90% uncertainty radius of 2.6 arcmin. The source is not classified, and the EP team notes that a stellar flare from G 2-7 within the WXT error circle cannot be ruled out.
Wavelength coverage
- X-ray: EP-WXT detected the transient; EP-FXT observed the field about 13.5 hours later for 2825 s and found no significant X-ray source, with a 0.5-10 keV flux upper limit of 7.55e-14 erg/cm^2/s.
- Optical: MASTER-SAAO, MASTER-OAFA, and MASTER-Tunka obtained clear-band observations with upper limits reaching up to 19.2 mag; no optical transient detection is reported.
No gamma-ray, radio, neutrino, or gravitational-wave observations are mentioned.
Lightcurve and spectrum
- The WXT transient lasted around 350 s during a roughly 700 s exposure.
- Short-timescale variation was observed during the WXT exposure.
- The WXT detection flux was about 4.81e-11 erg/cm^2/s.
- The average WXT 0.5-4 keV spectrum was fit with an absorbed power law with NH = 0.78(-0.59/+1.26) x 10^22 cm^-2 and photon index 3.07(-1.75/+4.08).
- The derived average unabsorbed 0.5-4 keV flux was 2.23(-1.47/+54.17) x 10^-10 erg s^-1 cm^-2.
- No significant EP-FXT source was detected 13.5 hours after the WXT detection.
Redshift
What’s special vs typical
- The event is notable as a short-duration, apparently new soft X-ray transient with rapid disappearance in later X-ray follow-up.
- Its astrophysical significance is uncertain because a stellar flare counterpart remains possible and no optical counterpart or redshift is reported.