On the High Energy Emission of the Short GRB 090510

Understand

Long-lived high-energy (>100MeV) emission, a common feature of most Fermi-LAT detected gamma-ray burst, is detected up to \sim 10^2 s in the short GRB 090510.

• We study the origin of this long-lived high-energy emission, using broad-band observations including X-ray and optical data.
• We confirm that the late > 100 MeV, X-ray and optical emission can be naturally explained via synchrotron emission from an adiabatic forward shock propagating into a homogeneous ambient medium with low number density.
• The Klein-Nishina effects are found to be significant, and effects due to jet spreading and magnetic field amplification in the shock appear to be required.