GeV Emission during X-Ray Flares from Late Internal Shocks: Application to GRB 100728A

Recently, the GeV radiation during the X-ray flare activity in GRB 100728A was detected by Feimi/LAT. Here we study the dynamics and emission properties of collision between two homogeneous shells based on the late internal shock model. The GeV photons can be produced from X-ray flare photons up-scattered by relativistic electrons accelerated by forward-reverse shocks, where involved radiative processes include synchrotron self-Compton and crossing inverse-Compton scattering. By analytical and numerical calculations, the observed spectral properties in GRB 100728A can be well explained.