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

Abstract

We report on the abundances of 13 elements in the planetary host HD 13189, a massive 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 yet discovered. Abundance ratios relative to Fe show no peculiarities with respect to random field stars. A census of metallicities of the seven currently known planet-harboring giants results in a distribution that is more metal-poor than the well-known metal-rich distribution of main sequence (MS) planetary hosts. This finding is discussed in terms of accretion of H-depleted material, one of the possible mechanisms responsible for the high-metallicity distribution of MS stars with planets. We estimate the mass of the HD 13189 progenitor to be 3.5 M ⊙ but cannot constrain this value to better than 2-6 M⊙. A stellar mass of 3.5 M⊙ implies a planetary mass of m sin i = 14.0 ± 0.8 MJ, placing the companion at the planet/brown dwarf boundary. Given its physical characteristics, the HD 13189 system is potentially unique among planetary systems, and its continued investigation should provide invaluable data to extrasolar planetary research. Subject headings: stars:individual (HD 13189) — planetary systems — stars:earlytype — stars:abundances — stars:atmospheres — stars:fundamental parameters 1Based on observations obtained at the 2-m Alfred Jensch telescope at the Thüringer Landessternwarte