Chemical Composition of the Planet-harboring Star TrES-1

Abstract

We present a detailed chemical abundance analysis of the parent star of the transiting extrasolar planet TrES-1. Based on high-resolution Keck HIRES and Hobby-Eberly Telescope HRS spectra, we have determined abundances relative to the Sun for 16 elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, and Ba). The resulting average abundance of = -0.02 ± 0.06 is in good agreement with initial estimates of solar metallicity based on iron. We compare the elemental abundances of TrES-1 with those of the sample of stars with planets, searching for possible chemical abundance anomalies. TrES-1 appears not to be chemically peculiar in any measurable way. We investigate possible signs of selective accretion of refractory elements in TrES-1 and other stars with planets and find no statistically significant trends of metallicity [X/H] with condensation temperature Tc. We use published abundances and kinematic information for the sample of planet-hosting stars (including TrES-1) and several statistical indicators to provide an updated classification in terms of their likelihood to belong to either the thin disk or the thick disk of the Milky Way. TrES-1 is found to be very likely a member of the thin-disk population. By comparing α-element abundances of planet hosts and a large control sample of field stars, we also find that metal-rich ([Fe/H] 0.0) stars with planets appear to be systematically underabundant in [α/Fe] by ≈0.1 dex with respect to comparison field stars. The reason for this signature is unclear, but systematic differences in the analysis procedures adopted by different groups cannot be ruled out.