High-Resolution Spectroscopy of the Planetary Host HD 13189: Highly Evolved and Metal-poor

We report on the abundances of 13 elements in the planetary host HD 13189, amassive giant star. Abundances are found to be sub-solar, with [Fe/H] = -0.58+/- 0.04$; HD 13189 is one of the most metal-poor planetary hosts yetdiscovered. Abundance ratios relative to Fe show no peculiarities with respectto random field stars. A census of metallicities of the seven currently knownplanet-harboring giants results in a distribution that is more metal-poor thanthe well-known metal-rich distribution of main sequence (MS) planetary hosts.This finding is discussed in terms of accretion of H-depleted material, one ofthe possible mechanisms responsible for the high-metallicity distribution of MSstars with planets. We estimate the mass of the HD 13189 progenitor to be 3.5M_sun but cannot constrain this value to better than 2-6 M_sun. A stellar massof 3.5 M_sun implies a planetary mass of m sin i = 14.0 +/- 0.8 M_J, placingthe companion at the planet/brown dwarf boundary. Given its physicalcharacteristics, the HD 13189 system is potentially unique among planetarysystems, and its continued investigation should provide invaluable data toextrasolar planetary research.Comment: 14 pages, 2 figures; Accepted for publication in ApJ Letter