Echo Emission From Dust Scattering and X-Ray Afterglows of Gamma-Ray Bursts

TL;DR

This paper explores how X-ray echo emission caused by dust scattering can explain various features of gamma-ray burst afterglows, offering new insights into the environment around GRB progenitors.

Contribution

It introduces the concept that dust-scattered X-ray echoes can account for observed afterglow behaviors and provides a method to measure properties of the progenitor's wind bubble.

Findings

X-ray echo emission can explain shallow and rapid decay phases.

Fitting light curves reveals properties of the progenitor's wind bubble.

Introduces an extra temporal break in the echo emission model.

Abstract

We investigate the effect of X-ray echo emission in gamma-ray bursts (GRBs). We find that the echo emission can provide an alternative way of understanding X-ray shallow decays and jet breaks. In particular, a shallow decay followed by a "normal" decay and a further rapid decay of X-ray afterglows can be together explained as being due to the echo from prompt X-ray emission scattered by dust grains in a massive wind bubble around a GRB progenitor. We also introduce an extra temporal break in the X-ray echo emission. By fitting the afterglow light curves, we can measure the locations of the massive wind bubbles, which will bring us closer to finding the mass loss rate, wind velocity, and the age of the progenitors prior to the GRB explosions.