GRB 260101A

General information

GRB 260101A is a long-duration, multi-peaked gamma-ray burst detected by multiple high-energy missions (notably Swift and Fermi) with a promptly identified X-ray and UV/optical afterglow. Early spectroscopy measured a secure redshift, enabling rest-frame energetics estimates.

Wavelength coverage

• Gamma-rays/hard X-rays: Detected by Fermi/GBM, Swift/BAT, SVOM/GRM, GECAM-B, Konus-Wind, and 239Alferov; multiple teams report prompt light curves and spectral fits.
• X-rays: Swift/XRT reports afterglow spectroscopy and a late-time power-law decay; (note: separate Einstein Probe EP260101a circulars refer to an X-ray transient at different coordinates).
• UV/optical: Swift/UVOT detects the afterglow in u/b/v; ground-based detections and limits reported by LCO (r′), GTC (r-band acquisition + spectra), NOT (acquisition + spectrum), COLIBRÍ (r and z), and MASTER-Net limits. No observations were mentioned for radio, infrared, or TeV/GeV (LAT) follow-up.

Lightcurve and spectrum

• Duration: T90 ≈ 27.4 s (Fermi/GBM, 50–300 keV), ≈ 30 s (GECAM-B), ≈ 33 s (SVOM/GRM), and T90 = 48 ± 16 s (Swift/BAT, 15–350 keV).
• Prompt spectra: Reported as cutoff power-law / CPL-like fits with Epeak ∼ 109–176 keV (Swift/BAT refined: Epeak ~109 keV; Fermi/GBM: Epeak ~143.5 keV; Konus-Wind CPL Ep ~176 keV time-integrated).
• Prompt fluence/flux: Fermi/GBM fluence (10–1000 keV) ≈ 6.7×10^-6 erg cm^-2; Konus-Wind fluence (20 keV–10 MeV) ≈ 7.47×10^-6 erg cm^-2 and 64-ms peak flux ≈ 1.95×10^-6 erg cm^-2 s^-1; Swift/BAT fluence (15–150 keV) ≈ 4.5×10^-6 erg cm^-2.
• X-ray afterglow: Swift/XRT late-time decay index α ≈ 1.65; photon index ≈ 1.9–2.0 with absorption consistent with (or only marginally above) Galactic.
• Optical/UV photometry: UVOT detections in u/b/v at early times (e.g., u≈16.1; b≈16.6–17.8; v≈15.9–17.2 in early exposures). Ground-based detections include LCO r′≈17.67 at ~59 min and GTC r≈18.05 at ~1.29 hr; later COLIBRÍ detects r≈22.11, z≈21.47 at ~50 h and reports fading beyond r>22.96, z>22.42 at ~99–101 h.

Redshift

• z = 2.623 from GTC/OSIRIS+ spectroscopy, identifying multiple absorption features at a common redshift; follow-up NOT spectroscopy notes consistent absorption features and highlights weak Ly-α.

What’s special vs typical

• The reported Ly-α absorption is unusually weak for the inferred z=2.623 sight line, noted as a peculiar aspect of the spectrum.
• Unusually broad reporting across many prompt instruments (including commissioning educational CubeSat data) provides redundant prompt measurements.