General information
EP260213a is a fast X-ray transient detected by Einstein Probe/WXT on 2026-02-13 with a duration of ~40 s, followed by an autonomous EP/FXT observation that detected an uncatalogued X-ray source within the WXT region.
Wavelength coverage
- X-ray: EP/WXT trigger and spectral/flux characterization; EP/FXT detection with refined position and spectrum/flux.
- Optical: Multiple facilities reported only upper limits in g/r/i/z (and related channels), including SVOM/C-GFT, NUTTelA-TAO, Mondy (R), SVOM/VT, SLT, COLIBRÍ, MASTER-Net, Liverpool Telescope, and Mephisto.
No gamma-ray, UV, IR, radio, neutrino, or GW observations are mentioned in the provided circulars.
Lightcurve and spectrum
- WXT: event start time reported at T0=2026-02-13T19:58:00 UTC; duration ~40 s; absorbed power-law fit (fixed NH=5.60e20 cm^-2) with photon index 0.6 ± 0.6; average unabsorbed 0.5–4 keV flux 1.4(-0.4/+0.5)e-9 erg s^-1 cm^-2.
- FXT: observation began 2026-02-13T20:03:06 UTC (~5 min after T0), exposure ~4.7 ks; absorbed power-law fit (fixed NH=5.60e20 cm^-2) with photon index 2.18(-0.15/+0.16); average unabsorbed 0.5–10 keV flux 1.77(-0.17/+0.19)e-12 erg cm^-2 s^-1.
- Optical: non-detections reported from minutes to ~16 hr post-trigger, including limits as deep as r>24.0 (5σ) and VT_B>23.7 / VT_R>23.5 (3σ).
Redshift
What’s special vs typical
- Strong X-ray fading is implied by the reported WXT (early, bright) versus FXT (minutes later, much fainter) flux measurements, while numerous rapid and deep optical follow-ups still report no counterpart.