GRB 260126A

General information

Einstein Probe reported a fast X-ray transient (EP260126a / GRB 260126A) starting 2026-01-26 04:25:01 UTC and lasting about 1400 s, with an uncatalogued FXT X-ray source detected in follow-up within the WXT error circle. Extensive optical follow-up reported only upper limits with no transient identified inside the refined FXT localization.

Wavelength coverage

• X-ray (0.5–4 keV; 0.5–10 keV): EP-WXT detection and EP-FXT follow-up detection with spectral fits and fluxes (GCN 43520; GCN 43526).
• Optical (g/r/i/z, VT_B/VT_R): multiple facilities reported non-detections with limits to r24.3 and g23.0–23.4 (GCN 43521; 43522; 43523; 43524; 43525; 43541; 43551). No observations were mentioned in gamma-ray, radio, infrared, ultraviolet, or neutrino/GW channels.

Lightcurve and spectrum

• Duration: ~1400 s (EP-WXT; GCN 43520).
• Spectral model (WXT, 0.5–4 keV): absorbed power law, photon index 1.16(-/+0.17) with NH fixed to Galactic 1.21e21 cm^-2 (GCN 43520).
• Flux/peak flux (WXT, unabsorbed 0.5–4 keV): average 2.77(-0.26/+0.29)e-10 erg/s/cm^2; peak 1.49(-0.14/+0.16)e-9 erg/s/cm^2 (GCN 43520).
• Spectral model (FXT, 0.5–10 keV): absorbed power law, photon index 1.76 +/- 0.20 with NH fixed to Galactic 1.21e21 cm^-2 (GCN 43526).
• Flux (FXT, unabsorbed 0.5–10 keV): ~5.65(+1.0/-0.85)e-13 erg/s/cm^2 (GCN 43526).

Redshift

What’s special vs typical

• Deep, multi-facility optical non-detections (to r~24) despite an X-ray detection and candidate refined FXT counterpart position suggest an optically faint or obscured transient scenario (GCN 43521; 43522; 43523; 43524; 43551).