GRB160203A: an exploration of lumpy space

TL;DR

This paper investigates the unusual afterglow features of GRB160203A, suggesting density fluctuations in the surrounding medium as the cause, linked to the host galaxy's properties and the progenitor environment.

Contribution

It provides a detailed analysis of the afterglow light curve, proposing density fluctuations as the explanation for flares, and links these to the host galaxy and progenitor environment.

Findings

Afterglow occurs in a constant density medium initially

Flares are caused by fluctuations in surrounding medium density

Energy injection and microphysical variations are unlikely explanations

Abstract

GRB160203A is a high redshift long gamma-ray burst presenting a collection of unusual features in the afterglow light curve. We study its optical and X-ray data. We find this event to occur within a constant density medium during the first part of the afterglow. However, after 13 ks we spot some flaring activities in the optical and X-ray light curves. We explain these flares by fluctuation of densities of the surrounding medium. Other scenarios, such as energy injection from a magnetar or variation of microphysical parameters are not supported by the data. We tentatively link these fluctuations to an unusual host galaxy, with gas density similar to the Milky Way and a dense cocoon of matter around a stellar progenitor similar to a Wolf-Rayet star. A termination shock scenario is found to be less likely.