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

JOFRE E.; PETRUCCI, R.; GOMEZ MAQUEO, Y.; DÍAZ, R. F.; SAFFE, C; GOMEZ, M.; BUCCINO, A.

Puerto Vallarta

Congreso; NEW QUESTS IN STELLAR ASTROPHYSICS IV; 2019

Radial velocity surveys have revealed a dearth of close-in planets (a < 0.5 AU; P < 100 days) around evolved stars. Close-in planets might be destroyed as they spiral into their hoststars as a result of tidal interactions [4]. Alternatively, planet formation and evolution mechanisms around more massive stars could produce a lower frequency of short-period gas giant planets. To date, based on high-precision Kepler photometry, only a handful of close-in (0.06 < a < 0.3 AU) transiting planets have been discovered around evolved stars on the red giant branch. Detailed characterization of these planetary systems is crucial for constraining models of planet-star interaction and planet formation in stars more massive than the Sun. In this context, we present a detailed stellar and planetary study of the exceptional systems Kepler-278 and Kepler-391. These are two of the only four multi-planet systems known to date that transit RGB stars. Our characterization includes the first determination of refined stellar parameters and precise photospheric chemical abundances based on high-quality spectra. In addition, from our newly measured stellar parameters, we obtained improved planetary properties.