Gemini-GRACES high-resolution spectroscopy of Kepler evolved stars with transiting planets

E. JOFRÉ, C. SAFFE, R. F. DÍAZ, R. PETRUCCI, E. MATIOLI, L. GARCÍA, M. GOMEZ

Malargüe

Congreso; 60 Reunión Anual de la Asociación Argentina de Astronomía; 2017

Asociación Argentina de Astronomía

Our knowledge of accurate physical properties of exoplanets, and hence the understanding of planetary structure and composition, is strongly linked to our knowledge of a series of fundamental parameters of their host stars. Specifically, the mass and radius of a transiting planet depend critically on the mass and radius of the parent star, since the photometric transit technique provides the planetary radius relative to the stellar radius and radial velocity observations only constrain the mass of the planet if we know the stellar mass. These physical stellar properties, in turn, depend on the precise measurement of the atmospheric parameters of the star (effective temperature, surface gravity, and metallicity), which can be derived from high-quality spectra. However, this kind of spectra are not commonly available for faint planet host stars such as those in the Kepler field. On the other hand, detailed spectroscopic chemical abundances of planet host stars are key to understanding the effects of refractory and volatile elements on the process of planet formation and evolution. Based on Gemini-GRACES high resolution and high signal-to-noise spectra, in this contribution we present the first detailed chemical composition analysis and improved stellar and planetary parameters of an evolved Kepler transiting multi-planet system without previous spectroscopic observations.