GRB 260119A

General information

Einstein Probe detected the fast X-ray transient EP260119a (GRB 260119A), with a confirmed optical afterglow and a measured high redshift. The event was widely followed up in X-rays and optical bands, including spectroscopy.

Wavelength coverage

• X-ray: Einstein Probe WXT detection; EP-FXT follow-up with spectral fits and flux estimates (GCN 43447, 43449, 43465).
• Optical/NIR: Afterglow detections and limits from multiple facilities in r/i/z/y and I/Ic/clear bands (e.g., GCN 43450, 43452, 43455, 43464, 43466, 43468, 43472, 43476, 43499, 43500). No observations were mentioned in: radio, mm/sub-mm, UV, GeV/TeV gamma-ray.

Lightcurve and spectrum

• Duration: WXT reports the transient lasted ~300 s (GCN 43447).
• X-ray spectrum (WXT, 0.5–4 keV): absorbed power law with photon index ~1.8 (-/+0.6) (GCN 43447).
• X-ray flux (WXT, 0.5–4 keV): average unabsorbed flux ~4.4e-11 erg s^-1 cm^-2; peak ~4.8e-10 erg s^-1 cm^-2 (GCN 43447).
• X-ray spectrum (FXT, 0.5–10 keV): absorbed power law with photon index 1.99 ± 0.13 (NH fixed to Galactic) (GCN 43465).
• X-ray flux (FXT, 0.5–10 keV): unabsorbed flux ~5.69 (+0.60/-0.55) x 10^-13 erg s^-1 cm^-2 (GCN 43465).
• Optical temporal behavior: COLIBRÍ reports a shallow z-band decay index of -0.44 ± 0.19 (GCN 43455).

Redshift

• z = 5.47 (spectroscopic): GTC/OSIRIS+ spectrum shows a sharp break around 7870 Å interpreted as the onset of the Lyman forest (GCN 43469).
• z = 5.62 (photometric): COLIBRÍ multi-filter photometry fit reports z = 5.62 with small formal errors (GCN 43455).

What’s special vs typical

• Secure high-redshift afterglow (z=5.47) based on spectroscopy, supported by an independent photometric redshift estimate (GCN 43469, 43455).
• Extremely red optical colors (strong r–z break) consistent with a Lyman-break/high-z interpretation (GCN 43450, 43452).