Fermi Observations of high-energy gamma-ray emissions from GRB 080916C

TL;DR

This paper reports Fermi observations of GRB 080916C, revealing a single spectral form across a wide energy range, delayed high-energy emission, and extreme energy release, providing insights into GRB physics and fundamental physics constraints.

Contribution

First detailed spectral and temporal analysis of a high-energy GRB across 8 keV to 13.2 GeV, establishing key physical parameters and constraints.

Findings

E>100 MeV emission delayed by ~5 s

Largest reported isotropic gamma-ray energy release (~8.8 x10^{54} ergs)

Lower limit on Lorentz factor (~890) and quantum gravity scale (>1.3 x10^{18} GeV/c^2)

Abstract

Observations of the long-duration Gamma-Ray Burst GRB 080916C by the Fermi Gamma-ray Burst Monitor and Large Area Telescope show that it has a single spectral form from 8 keV to 13.2 GeV. The E>100 MeV emission was ~5 s later than the E<1 MeV emission and lasted much longer even after photons with E<100 MeV became undetectable. The redshift from GROND of z~4.35 means that this GRB has the largest reported apparent isotropic gamma-ray energy release, E_{iso} ~ 8.8 x10^{54} ergs. It also sets a stringent lower limit on the GRB outflow Lorentz factor, Gamma_{min}~890, and limits the quantum gravity mass scale, M_{QG} > 1.3 x 10^{18} GeV/c^2.