2008/02/07 by S. Bradley Cenko, Cenko, S. Bradley, Edo Berger +25
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.0802.0874
ApJL submitted; 4 pages, 3 figures; Comments welcome
arxiv created 2008/02/07 · arxiv updated 2009/12/01
We present optical spectra of the host galaxies of the short-duration gamma-ray burst GRB 070429B and the likely short-duration with extended emission GRB 070714B. In both cases, we find a single emission line that we identify as O II lambda 3727 at z ~ 0.9. Both events are more distant than any previous short-duration GRB with a secure host association from the sub-arcsecond position of an optical afterglow. GRBs 070429B and 070714B provide strong evidence in support of our previous claims in Berger et al. that a significant fraction of short-duration hosts (>~ 33%) reside at z > 0.7. We discuss the implications of the existence this population on the energetics of short-duration GRBs, as well as on progenitor models. In the context of the degenerate binary merger scenario, such events require progenitor systems with a range of lifetimes and disfavor progenitor models with a long, narrow lifetime distribution.