High-energy emission: light curves. The light curves in the soft gamma-ray range (260 keV–5 MeV, left figure) and in the high-energy gamma-ray range (>1 GeV, right figure) are plotted for different cases discussed in the paper. For the high-energy light curves, a thin solid line indicates that the synchrotron emission is dominant above 1 GeV whereas a thick solid line indicates that the inverse-Compton emission is dominant. Top panel: reference Cases A and B; Second panel: Cases A and B with a varying accelerated electron fraction ζ; Third panel: Case B with a sharp initial distribution of the Lorentz factor (see text) and a constant or a varying accelerated electron fraction ζ; Bottom panel: Case B with a constant ejected mass flux (see text) and a constant or a varying accelerated electron fraction ζ.