Journal Article

Variable Lyα sheds light on the environment surrounding GRB 090426

C. C. Thöne, S. Campana, D. Lazzati, A. de Ugarte Postigo, J. P. U. Fynbo, L. Christensen, A. J. Levan, M. A. Aloy, J. Hjorth, P. Jakobsson, E. M. Levesque, D. Malesani, B. Milvang-Jensen, P. W. A. Roming, N. R. Tanvir, K. Wiersema, M. Gladders, E. Wuyts and H. Dahle

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 1, pages 479-488
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18408.x
Variable Lyα sheds light on the environment surrounding GRB 090426

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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 ionization 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 ionized medium together with a low column density of neutral hydrogen. For the first time, we also observe variations in the Lyα absorption line. Photoionization modelling 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.

Keywords: gamma-ray burst: general; X-rays: general; X-rays: ISM

Journal Article.  7366 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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