Behaviors of X-ray Dust-Scattering and Implications for X-ray Afterglows of Gamma-Ray Bursts

The afterglows of gamma-ray bursts (GRBs) have been commonly assumed to be due to shocks sweeping up circum-stellar medium. However, most of them have been found to be hosting in dense star-forming regions where a significant fraction of the prompt X-ray emission can be scattered by dust grains. Here we revisit the behaviors of X-ray dust-scattering in GRBs. We find that the features of some X-ray afterglows about minutes to days after the gamma-ray triggers are consistent with scattering of prompt X-ray emission from GRBs off host dust grains. This implies that some of the observed X-ray afterglows (especially those without sharp rising and decaying flares) could be understood in this dust-scattering-driven emission model