High-Resolution Spectroscopy of the Transiting Planet Host Star TrES-1

Abstract

We report on a spectroscopic determination of the stellar parameters and chemical abundances for the parent star of the transiting planet TrES-1. Based on a detailed analysis of iron lines in our Keck and HET spectra we derive $T_{\mathrm{eff}}=5250\pm 75$ K, $\log g=4.6\pm 0.2$, and [Fe/H] $=0.00\pm 0.09$. By measuring the \ion{Ca}{2} activity indicator and by putting useful upper limits on the Li abundance we constrain the age of TrES-1 to be $2.5\pm 1.5$ Gyr. By comparing theoretical stellar evolution models with the observational parameters we obtain $M_{\star }=0.89\pm 0.05$ $M_{\odot }$, and $R_{\star }=0.83\pm 0.05$ $R_{\odot }$. Our improved estimates of the stellar parameters are utilized in a new analysis of the transit photometry of TrES-1 to derive a mass $M_p=0.76\pm 0.05$ $M_{\mathrm{J}}$, a radius $R_p=1.04_{-0.05}^{+0.08}$ $R_{\mathrm{J}}$, and an inclination $i=89^{\circ }.5_{-1.3}^{+0.5}$. The improved planetary mass and radius estimates provide the grounds for new crucial tests of theoretical models of evolution and evaporation of irradiated extrasolar giant planets.

14 pages, 3 figures, Astrophysical Journal Letters, accepted