Program: GN-2017A-FT-20

In the context of exoplanet research, it is key to characterize the interior structure of exoplanets, in turn, such characterization requires a detailed knowledge of the chemical abundance of exoplanet hosts. There are only 14 exoplanets (around 11 stars) listed in the literature with a precise planetary mass derivation and that are smaller than about three times the radius of the Earth. Our team has collected high-quality spectra for seven of the hosts of these exoplanets. Here, we propose to obtain GRACES high-resolution and high-S/N spectra for two of the "missing" exoplanet hosts: I) Kepler-454, which hosts a planet located in the transition region between rocky and gaseous planets, and II) Kepler-93, that harbor one of the smallest and lightest planets detected so far. The spectra of these host stars, combined with previously collected data, will allow us to characterize the internal composition of most small exoplanets in detail and, hence, to make a meaningful and homogeneous comparison of their properties.