Journal Article

GRB 090426: the environment of a rest-frame 0.35-s gamma-ray burst at a redshift of 2.609

Emily M. Levesque, Joshua S. Bloom, Nathaniel R. Butler, Daniel A. Perley, S. Bradley Cenko, J. Xavier Prochaska, Lisa J. Kewley, Andrew Bunker, Hsiao-Wen Chen, Ryan Chornock, Alexei V. Filippenko, Karl Glazebrook, Sebastian Lopez, Joseph Masiero, Maryam Modjaz, Adam Morgan and Dovi Poznanski

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 401, issue 2, pages 963-972
Published in print January 2010 | ISSN: 0035-8711
Published online January 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15733.x
GRB 090426: the environment of a rest-frame 0.35-s gamma-ray burst at a redshift of 2.609

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We present the discovery of an absorption-line redshift of z= 2.609 for GRB 090426, establishing the first firm lower limit to a redshift for a gamma-ray burst (GRB) with an observed duration of <2 s. With a rest-frame burst duration of T90z= 0.35 s and a detailed examination of the peak energy of the event, we suggest that this is likely (at >90 per cent confidence) a member of the short/hard phenomenological class of GRBs. From analysis of the optical-afterglow spectrum we find that the burst originated along a very low H i column density sightline, with NH i < 3.2 × 1019 cm−2. Our GRB 090426 afterglow spectrum also appears to have weaker low-ionization absorption (Si ii, C ii) than ∼95 per cent of previous afterglow spectra. Finally, we also report the discovery of a blue, very luminous, star-forming putative host galaxy (∼2L*) at a small angular offset from the location of the optical afterglow. We consider the implications of this unique GRB in the context of burst duration classification and our understanding of GRB progenitor scenarios.

Keywords: galaxies: ISM; gamma-rays: bursts

Journal Article.  7684 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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