Effects of the upper cutoff of the electron distribution on the light curves of GRB afterglows

Abstract

We investigate the behaviour of the frequency centered light curves expected within the standard model of Gamma Ray Bursts after taking into account the maximum electron energy (γ max ) as an additional free parameter. First we consider cases where γ max is constant throughout the evolution of the afterglow and present the different X-ray lightcurve morphologies obtained for various ratios of the maximum to the miminum electron Lorenzt factor. As a second step we generalize our results by assuming that the maximum electron Lorentz factor varies with radius as a result of variable acceleration and loss timescales. We will discuss some of the results giving emphasis on the shape of the expected X-ray lightcurves and hardness ratios.