GRB 080916C: on the radiation origin of the prompt emission from KeV/MeV to GeV

Understand

Fermi observations of high-energy gamma-ray emission from GRB 080916C shows that its spectrum is consistent with the Band function from MeV to tens of GeV.

• Assuming one single emission mechanism dominates in the whole energy range, we show that this spectrum is consistent with synchrotron origin by shock-accelerated electrons.
• The simple electron inverse-Compton model and the hadronic model are found to be less viable.
• In the synchrotron scenario, the synchrotron self-Compton scattering is likely to be in the Klein-Nishina regime and therefore the resulting high-energy emission is subdominant, even though the magnetic field energy density is lower than that in relativistic electrons.