General information
GRB 260105B is a likely long gamma-ray burst detected by Fermi/GBM at 2026-01-05 23:21:36 UT and independently observed by SVOM/GRM. Follow-up reports include prompt-emission spectral/temporal properties and optical upper limits, and an Einstein Probe X-ray transient on the same date with uncertain association.
Wavelength coverage
- Gamma-ray: Fermi/GBM; SVOM/GRM.
- X-ray: Einstein Probe WXT/FXT reported an X-ray transient with a decaying FXT source (association with the GRB not established in the cited text).
- Optical: MASTER-Net reported only upper limits (clear filter).
No UV/IR, radio, TeV, neutrino, or GW observations are mentioned in the provided circulars.
Lightcurve and spectrum
- Duration: T90 ~11 s (Fermi/GBM, 50–300 keV); T90 = 6.8 (+1.8/-1.4) s (SVOM/GRM, 15–5000 keV).
- Prompt spectrum (Fermi/GBM): cutoff power-law with index -0.96 ± 0.01 and Epeak = 232 ± 2 keV; fluence (10–1000 keV) = (8 ± 0.4)×10^-6 erg cm^-2; 1 s peak photon flux (10–1000 keV) = 156 ± 2 ph s^-1 cm^-2.
- Prompt spectrum (Fermi/GBM, alternative): Band with Epeak = 178 ± 2 keV, alpha = -0.83 ± 0.01, beta = -2.19 ± 0.03.
- Prompt spectrum (SVOM/GRM): cutoff power-law with index -0.61 (+0.12/-0.13) and Epeak = 177 (+15/-13) keV; fluence (10–1000 keV) = (9.34+0.47/-0.44)×10^-6 erg cm^-2; 1 s flux (10–1000 keV) = (2.53 +0.22/-0.20)×10^-6 erg cm^-2 s^-1.
- X-ray (Einstein Probe/FXT): decaying light curve reported; absorbed power-law with photon index 2.18 (-0.87/+0.92) and average unabsorbed 0.5–10 keV flux 2.6 (-0.94/+2.59)×10^-13 erg s^-1 cm^-2 (Galactic NH fixed at 2.97×10^20 cm^-2).
Redshift
What’s special vs typical
- Very high reported 1 s peak photon flux (156 ± 2 ph s^-1 cm^-2 in 10–1000 keV) relative to many GBM GRBs.
- An EP X-ray transient initially thought to be a stellar flare was later reclassified as an X-ray transient; its relation to GRB 260105B is unclear in the provided reports.