Improving Stellar and Planetary Parameters of Transiting Planet Systems: The Case of TrES-2

Understand

We report on a spectroscopic determination of the atmospheric parameters and chemical abundance of the parent star of the recently discovered transiting planet {TrES-2}.

• A detailed LTE analysis of a set of \ion{Fe}{1} and \ion{Fe}{2} lines from our Keck spectra yields $T_\mathrm{eff} = 5850\pm 50$ K, $\log g = 4.4\pm 0.1$, and [Fe/H] $= -0.15\pm 0.10$.
• Several independent checks (e.g., additional spectroscopy, line-depth ratios) confirm the reliability of our spectroscopic $T_\mathrm{eff}$ estimate.
• The mass and radius of the star, needed to determine the properties of the planet, are traditionally inferred by comparison with stellar evolution models using $T_\mathrm{eff}$ and some measure of the stellar luminosity, such as the spectroscopic surface gravity (when a trigonometric parallax is unavailable, as in this case).