Super-Earths and sub-Neptunes are Insensitive to Stellar Metallicity
arXiv:2003.08431 · doi:10.3847/1538-3881/ac0431
Abstract
Kepler planets (including super-Earths and sub-Neptunes, from 1 to 4 Earth radii) are likely formed before the gaseous proto-planetary disks have dissipated, as are the Jovian planets. If the metal content in these disks resembles that in the host stars, one might expect Kepler planets to occur more frequently, and to be more massive, around metal-rich stars. Contrary to these expectations, we find that the radii of Kepler planets (a proxy for mass) are independent of host metallicity. Previous claims that larger planets prefer more metal-rich stars can be adequately explained by the combined facts that more massive stars tend to host bigger planets, and that more massive stars are also more metal rich in the Kepler sample. We interpret this independence as that the mass of a Kepler planet is not determined by the availability of solids, but is instead regulated by an as yet unknown process. Moreover, we find that the occurrence rates of Kepler planets rise only weakly with stellar metallicity, a trend that is further flattened when the influence of close stellar binaries is accounted for. We explain this weak dependence, in contrast to the strong dependence exhibited by Jovian planets, using a phenomenological model, wherein the masses of proto-planetary disks have a much larger spread than the spread in stellar metallicity, and wherein the formation of Jovian planets requires disks that contain some times more solid than that needed to form Kepler planets. This model predicts that stars more metal-poor than half-solar should rarely host any Kepler planets.
Accepted to AJ, major expansion on sample bias and completeness correction. Conclusions unchanged
References in corpus (22)
- New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
- Most 1.6 Earth-Radius Planets are not Rocky
- Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
- Separating gas-giant and ice-giant planets by halting pebble accretion
- The Geneva-Copenhagen Survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk
- Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
- Three regimes of extrasolar planets inferred from host star metallicities
- Formation of planetary systems by pebble accretion and migration: How the radial pebble flux determines a terrestrial-planet or super-Earth growth mode
- Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
- The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
- Influence of Stellar Multiplicity On Planet Formation. II. Planets Are Less Common in Multiple-Star Systems with Separations Smaller than 1500 AU
- Global Models of Planet Formation and Evolution
- On the Abundance of Circumbinary Planets
- Close Binary Companions to APOGEE DR16 Stars: 20,000 Binary-star Systems Across the Color-Magnitude Diagram
- LAMOST telescope reveals that Neptunian cousins of hot Jupiters are mostly single offspring of stars that are rich in heavy elements
- A Super-Solar Metallicity For Stars With Hot Rocky Exoplanets
- Signatures of unresolved binaries in stellar spectra: implications for spectral fitting
- The Densities of Planets in Multiple Stellar Systems
- Measuring Transit Signal Recovery in the Kepler Pipeline IV: Completeness of the DR25 Planet Candidate catalog
- Revisiting the Long-Period Transiting Planets from Kepler
- The Effect of Binarity on Circumstellar Disk Evolution
- A Distinct Population of Small Planets: Sub-Earths