Tanga, M., Schady, P., Gatto, A., Greiner, J., Krause, M. G. H., Diehl, R., Savaglio, S. and Walch, S. (2016). Soft X-ray absorption excess in gamma-ray burst afterglow spectra: Absorption by turbulent ISM. Astron. Astrophys., 595. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Two-thirds of long duration gamma-ray bursts (GRBs) show soft X-ray absorption in excess of the Milky Way. The column densities of metals inferred from UV and optical spectra differ from those derived from soft X-ray spectra, at times by an order of magnitude, with the latter being higher. The origin of the soft X-ray absorption excess observed in GRB X-ray afterglow spectra remains a heavily debated issue, which has resulted in numerous investigations on the effect of hot material both internal and external to the GRB host galaxy on our X-ray afterglow observations. Nevertheless, all models proposed so far have either only been able to account for a subset of our observations (i.e. at z > 2), or they have required fairly extreme conditions to be present within the absorbing material. In this paper, we investigate the absorption of the GRB afterglow by a collisionally ionised and turbulent interstellar medium (ISM). We find that a dense (3 cm(-3)) collisionally ionised ISM could produce UV/optical and soft X-ray absorbing column densities that differ by a factor of 10. However the UV/optical and soft X-ray absorbing column densities for such sightlines are 2-3 orders of magnitude lower in comparison to the GRB afterglow spectra. For those GRBs with a larger soft X-ray excess by up to an order of magnitude, the contribution in absorption from a turbulent ISM as considered here would ease the required conditions of additional absorbing components, such as the GRB circumburst medium and intergalactic medium.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Tanga, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Schady, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gatto, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Greiner, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Krause, M. G. H.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Diehl, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Savaglio, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Walch, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-256715
DOI: 10.1051/0004-6361/201527961
Journal or Publication Title: Astron. Astrophys.
Volume: 595
Date: 2016
Publisher: EDP SCIENCES S A
Place of Publication: LES ULIS CEDEX A
ISSN: 1432-0746
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
GRB HOST GALAXIES; SIMILAR-TO 2; STAR-FORMING GALAXIES; HIGH-RESOLUTION SPECTROSCOPY; COSMIC CHEMICAL EVOLUTION; SINS/ZC-SINF SURVEY; DAMPED LY-ALPHA; INTERSTELLAR-MEDIUM; COLUMN DENSITIES; MOLECULAR-HYDROGENMultiple languages
Astronomy & AstrophysicsMultiple languages
Refereed: Yes
URI: http://kups.ub.uni-koeln.de/id/eprint/25671

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