A Putative Early-Type Host Galaxy for GRB 060502B: Implications for the Progenitors of Short-Duration Hard-Spectrum Bursts

Abstract

Starting with the first detection of an afterglow from a short-duration hard-spectrum gamma-ray burst (SHB) by Swift last year, a growing body of evidence has suggested that SHBs are associated with an older and lower-redshift galactic population than long-soft GRBs and, in a few cases, with large (>~ 10 kpc) projected offsets from the centers of their putative host galaxies. Here we present observations of the field of GRB 060502B, a SHB detected by Swift and localized by the X-ray Telescope (XRT). We find a massive red galaxy at a redshift of z=0.287 at an angular distance of 17.1 arcsec from our revised XRT position. Using associative and probabilistic arguments we suggest that this galaxy hosted the progenitor of GRB 060502B. If true, this offset would correspond to a physical displacement of 73 +- 19 kpc in projection, about twice the largest offset inferred for any SHB to date and almost an order of magnitude larger than a typical long-soft burst offset. Spectra and modeling of the star-formation history of this possible host show it to have undergone a large ancient starburst. If the progenitor of GRB 060502B was formed in this starburst episode, the time of the GRB explosion since birth is tau = 1.3 +- 0.2 Gyr and the minimum kick velocity of the SHB progenitor is v_kick = 55 +- 15 km/s.

Accepted to the Astrophysical Journal. 18 pages, 3 figures; expanded discussion of alternative host possibilities

References in corpus (1)

• The faint afterglow and host galaxy of the short-hard GRB 060121

Cited by in corpus (13)

• Discerning the physical origins of cosmological Gamma-ray bursts based on multiple observational criteria: the cases of z=6.7 GRB 080913, z=8.3 GRB 090423, and some short/hard GRBs
• Implications for the Origin of GRB 070201 from LIGO Observations
• Type Ia Supernovae are Good Standard Candles in the Near Infrared: Evidence from PAIRITEL
• A Comparison of the Afterglows of Short- and Long-Duration Gamma-Ray Bursts
• The Host Galaxies of Short-Duration Gamma-Ray Bursts: Luminosities, Metallicities, and Star Formation Rates
• Different progenitors of short hard gamma-ray bursts
• The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts
• A case of mistaken identity? GRB 060912A and the nature of the long -- short GRB divide
• Refined Astrometry and Positions for 179 Swift X-ray Afterglows
• The short GRB070707 afterglow and its very faint host galaxy
• On the nature of the short duration GRB 050906
• Constraints on an optical afterglow and on supernova light following the short burst GRB 050813
• Intracluster Short Gamma-Ray Bursts by Compact Binary Mergers