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 \approx 5 s later than the E \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 1 MeV emission and lasted much longer even after photons with E < 100 MeV became undetectable .
The redshift from GROND of z \approx 4.35 means that this GRB has the largest reported apparent isotropic \gamma -ray energy release , E _ { \mathrm { iso } } \approx 8.8 \times 10 ^ { 54 } ergs .
It also sets a stringent lower limit on the GRB outflow Lorentz factor , \Gamma _ { min } \approx 890 , and limits the quantum gravity mass scale , M _ { QG } > 1.3 \times 10 ^ { 18 } GeV / c ^ { 2 } .