GRB 251214B

General information

GRB 251214B is a long-duration gamma-ray burst detected by Swift/BAT and Fermi/GBM (also reported by GECAM-B) with a rapidly identified X-ray and UV/optical afterglow.

Wavelength coverage

• Gamma-rays: prompt emission reported by Swift/BAT, Fermi/GBM, and GECAM-B.
• X-rays: Swift/XRT detected a fading X-ray counterpart and reported refined position and light-curve/spectral fits.
• UV/optical: Swift/UVOT detected the afterglow; extensive ground-based optical imaging follow-up reported detections and upper limits.
• Optical/NIR spectroscopy: VLT/X-shooter obtained a spectrum (no secure host emission features reported). No observations were mentioned in radio or (sub-)mm bands.

Lightcurve and spectrum

• Swift/BAT: T90(15–350 keV) = 9.38 ± 0.73 s; time-averaged power-law index = 1.79 ± 0.12; 15–150 keV fluence = (5.0 ± 0.4)×10^-7 erg/cm^2; 1-s peak photon flux (15–150 keV) = 2.0 ± 0.2 ph/cm^2/s. (GCN 43129)
• Fermi/GBM: T90(50–300 keV) ~ 15 s; cutoff power-law with index = −1.81 ± 0.05 and Epeak = 1280 ± 80 keV; 10–1000 keV fluence = (1.3 ± 0.1)×10^-6 erg/cm^2. (GCN 43120)
• GECAM-B: T90 = 17.7 (+1.8/−1.2) s (70–6000 keV). (GCN 43113)
• Swift/XRT: light curve decay alpha = 0.72 (+0.14/−0.17) with a break at T+418 s to alpha = 1.33 (+0.10/−0.08); absorbed power-law photon index = 1.82 (+0.19/−0.18) with total NH = 1.6 (+0.7/−0.6)×10^21 cm^-2 (excess over Galactic). (GCN 43112)

Redshift

• A likely host galaxy coincident with the afterglow is reported with photometric redshift z ≈ 0.70 ± 0.07 (Legacy Survey phot-z). (GCN 43103)
• A photometric redshift of z = 0.709 ± 0.078 is also cited for the likely host contribution in optical photometry. (GCN 43123)

What’s special vs typical

• Likely low-redshift (photometric) host-candidate at z ~ 0.70, and VLT/X-shooter notes complex underlying source structure (two "blobs"). (GCN 43103, GCN 43131)