Variable Ly alpha sheds light on the environment surrounding GRB 090426
Abstract
Long duration gamma-ray bursts are commonly associated with the deaths of massive stars. Spectroscopic studies using the afterglow as a light source provide a unique opportunity to unveil the medium surrounding it, probing the densest region of their galaxies. This material is usually in a low ionisation state and at large distances from the burst site, hence representing the normal interstellar medium in the galaxy. Here we present the case of GRB 090426 at z=2.609, whose optical spectrum indicates an almost fully ionised medium together with a low column density of neutral hydrogen. For the first time, we also observe variations in the Ly alpha absorption line. Photoionisation modeling shows that we are probing material from the vicinity of the burst (~80 pc). The host galaxy is a complex of two luminous interacting galaxies, which might suggest that this burst could have occurred in an isolated star-forming region outside its host galaxy created in the interaction of the two galaxies.
Cite
@article{arxiv.1101.3488,
title = {Variable Ly alpha sheds light on the environment surrounding GRB 090426},
author = {C. C. Thöne and S. Campana and D. Lazzati and A. de Ugarte Postigo and J. P. U. Fynbo and L. Christensen and A. J. Levan and M. A. Aloy and J. Hjorth and P. Jakobsson and E. M. Levesque and D. Malesani and B. Milvang-Jensen and P. W. A. Roming and N. R. Tanvir and K. Wiersema and M. Gladders and E. Wuyts and H. Dahle},
journal= {arXiv preprint arXiv:1101.3488},
year = {2015}
}
Comments
11 pages, 9 figures, submitted to MNRAS