Wednesday 04 Nov 2020: [Seminar] The influence of stellar metallicity and mass on the formation, evolution and architectures of planetary systems
Luan Ghezzi - Observatorio do Valongo, Rio de Janeiro
Reomte seminar 14:00-15:00
Correlations between stellar and planetary properties provide important information about the processes of planet formation and evolution and the resulting architectures of planetary systems. It is already known that higher metallicities and masses favor the formation of giant planets around FGK dwarfs and subgiants. However, it is not clear whether these correlations hold for neptunian and terrestrial planets. In this talk, I will describe how we are addressing these questions through a detailed spectroscopic analysis of two samples: 245 subgiants ("retired A stars") monitored for the presence of planets as part of the Lick and Keck planet survey and 1005 stars with planets detected by the Kepler mission and observed by the California Keck Survey (CKS). As a result of the study of the subgiants, we confirmed that giant planet occurrence increases with both stellar metallicity and mass up to ~2.0 M_Sun. Moreover, we showed that the probability of forming a giant planet is an almost linear function of the total amount of metals in the protoplanetary disk, which provides further support to the core accretion model for planet formation. As a result of the study of the CKS sample, we observed that metallicities of stars hosting Sub-Saturns and Jupiters (Rp >= 4.4 R_Earth) are significantly skewed to higher values, while systems having only Super-Earths and Sub-Neptunes (Rp < 4.4 R_Earth) orbit stars having a metallicity distribution that is very similar to that of the Galactic thin disk in the solar neighborhood. Host star metallicity distributions differ between hot and warm planetary systems, with the former being more metal-rich. This effect seems to be larger for multiple relative to single systems and the most significant differences are seen for stars hosting only Super-Earths. These results show that the stellar metallicity has a fundamental role in determining the architectures of planetary systems.