Stellar and planetary characterization of two Kepler multi-planet systems from high-quality Gemini/GRACES spectra

MARTIOLI, E.; SAFFE, C; GÓMEZ, M.; PETRUCCI, R.; JOFRÉ, E; GÓMEZ MAQUEO, C.; RAMÍREZ, I.; DIAZ, R. F.; BUCCINO, A P

Workshop; Sagan Exoplanet Summer Workshop; 2018

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 data is 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 can provide important constraints for the models of planet formation and evolution. Based on Gemini-GRACES high resolution and high signal-to-noise spectra, in this contribution, we report improved stellar and planetary parameters of two evolved Kepler multi-planet systems. In addition, we present a stellar activity and detailed chemical composition analysis of the host stars.