GRB 251214A

General information

GRB 251214A was detected in gamma rays (Fermi/GBM) and followed by an Einstein Probe WXT X-ray transient (EP251214a) observed about two hours later, suggested as a possible X-ray afterglow. Subsequent X-ray and optical follow-up reported only upper limits, with notably deep optical non-detections.

Wavelength coverage

• Gamma-ray/hard X-ray: Fermi/GBM (detection); GECAM-B (detection); AstroSat CZTI (detection).
• Soft X-ray: Einstein Probe WXT (detection); Einstein Probe FXT (non-detection / upper limit at ~13 hr after WXT).
• Optical/NIR: Multiple facilities (COLIBRÍ, KAIT, MASTER-Net, Lulin SLT) report non-detections with limiting magnitudes down to r>23.1. No observations mentioned in: radio, millimeter/sub-mm, UV, GeV (LAT/CTA).

Lightcurve and spectrum

• EP-WXT: absorbed power-law fit with photon index 1.84 (±0.94); average unabsorbed 0.5–4 keV flux 1.05 (−0.42/+0.70) × 10^-11 erg cm^-2 s^-1.
• GECAM-B: T90 ≈ 5.0 (+1.0/−2.5) s (70–6000 keV).
• AstroSat CZTI: T90 ≈ 1.4 (+0.2/−1.0) s in 20–200 keV (partial detection of brighter short-duration component).
• EP-FXT: 0.5–10 keV upper limit ≈ 7×10^-14 erg cm^-2 s^-1.

Redshift

What’s special vs typical

• Deep early optical non-detections (e.g., r>23.1 at ~7–8 hr) alongside an X-ray transient candidate are consistent with a dark afterglow/FXT-like behavior.