Behavior of X-ray dust scattering and implications for X-ray afterglows of gamma-ray bursts

The afterglows of gamma-ray bursts (GRBs) have commonly been assumed to be due to shocks sweeping up the circumstellar medium. However, most GRBs have been found 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 behavior of dust scattering of X-rays in GRBs. We find that the features of some X-ray afterglows from minutes to days after the gamma-ray triggers are consistent with the 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 with a dust-scattering-driven emission model.