UVES-VLT High Resolution Spectroscopy of GRB080319B and GRB080330 Afterglows

TL;DR

This study uses high-resolution spectroscopy to analyze the complex interstellar medium around two GRBs, revealing the distances of gas from the explosion site and the influence of GRB radiation on their host galaxies.

Contribution

It provides detailed measurements of gas distances from GRB sites using UVES spectra, highlighting the impact of GRB radiation on surrounding interstellar medium.

Findings

Gas is 2-6 kpc from GRB080319B

Gas is approximately 280 pc from GRB080330

GRB radiation influences ISM up to several hundred parsecs

Abstract

We study here the Gamma-Ray Burst (GRB) environment through the analysis of the optical absorption features due to the gas surrounding the GRB. In particular, we analyze high resolution spectroscopic observations of GRB080319B and GRB080330 taken with UVES at the VLT, starting 8m30s and 1.5hr after the GRB trigger, respectively. The spectra show that the ISM of the GRB host galaxies are complex, with several components contributing to the host absorption system. In addition, we detect strong excited absorption lines, from which we derive information on the gas distance from the site of the GRB explosion. Under the assumption that the excited features are produced by indirect UV pumping, we found that this distance results to be 2-6 kpc for GRB080319B and 280+/-50 pc for GRB080330, meaning that the power of the GRB radiation can influence the conditions of the interstellar medium up to a distance of several hundred pc.