On Dust Extinction of Gamma-ray Burst Host Galaxies

TL;DR

This paper introduces an analytical formula to better model dust extinction in gamma-ray burst host galaxies, addressing discrepancies in previous methods and improving the understanding of dust properties affecting afterglow observations.

Contribution

It proposes a new analytical approach to derive GRB host galaxy extinction laws, overcoming limitations of template-based models and revealing diverse dust extinction behaviors.

Findings

The new formula can fit a variety of extinction laws beyond standard templates.

Application to afterglow data shows improved consistency with dust depletion and X-ray studies.

The method enables more accurate determination of dust properties in GRB host galaxies.

Abstract

Although it is well recognized that gamma-ray burst (GRB) afterglows are obscured and reddened by dust in their host galaxies, the wavelength-dependence and quantity of dust extinction are still poorly known. Current studies on this mostly rely on fitting the afterglow spectral energy distributions (SEDs) with template extinction models. The inferred extinction (both quantity and wavelength-dependence) and dust-to-gas ratios are often in disagreement with that obtained from dust depletion and X-ray spectroscopy studies. We argue that this discrepancy could result from the prior assumption of a template extinction law. We propose an analytical formula to approximate the GRB host extinction law. With the template extinction laws self-contained, and the capability of revealing extinction laws differing from the conventional ones, it is shown that this is a powerful approach in modeling the afterglow SEDs to derive GRB host extinction.