No Metallicity Correlation Associated with the Kepler Dichotomy

Abstract

NASA's Kepler mission has discovered thousands of planetary systems, ~20% of which are found to host multiple transiting planets. This relative paucity (compared to the high fraction of single transiting systems) is postulated to result from a distinction in the architecture between multi-transiting systems and those hosting a single transiting planet: a phenomenon usually referred to as the Kepler dichotomy. In this paper, we investigate the hypothesis that external giant planets are the main cause behind the over-abundance of single- relative to multi-transiting systems, which would be signaled by higher metallicities in the former sample. To this end, we perform a statistical analysis on the stellar metallicity distribution with respect to planet multiplicity in the Kepler data. We perform our analysis on a variety of samples taken from a population of 1166 Kepler main sequence planetary hosts, using precisely determined metallicities from the California-Kepler survey and Swift et al. (2015). Contrary to some predictions, we do not find a significant difference between the stellar metallicities of the single- and multiple-transiting planet systems. However, we do find a 55% upper bound for systems with a single non-giant planet that could also host a hidden giant planet, based on metallicity considerations. While the presence of external giant planets might be one factor behind the Kepler dichotomy, our results also favor alternative explanations. We suggest that additional radial velocity and direct imaging measurements are necessary to constrain the presence of gas giants in systems with a single transiting planet.

Accepted in The Astronomical Journal, 9 pages, 4 figures

References in corpus (9)

• Three regimes of extrasolar planets inferred from host star metallicities
• Exploring Exoplanet Populations with NASA's Kepler Mission
• Precise Radial Velocities of Giant Stars VII. Occurrence Rate of Giant Extrasolar Planets as a Function of Mass and Metallicity
• Evolved stars hint to an external origin of enhanced metallicity in planet-hosting stars
• A Statistical Reconstruction of the Planet Population Around Kepler Solar-Type Stars
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• Gas giant planets as dynamical barriers to inward-migrating super-Earths
• Spin-orbit Misalignment as a Driver of the Kepler Dichotomy
• Sterile and Fertile Planetary Systems - Statistical Analysis of Multi-Planet Systems in Kepler's data

Cited by in corpus (9)

• Exoplanet Statistics and Theoretical Implications
• Accounting for Incompleteness due to Transit Multiplicity in Kepler Planet Occurrence Rates
• The California-Kepler Survey. VI: Kepler Multis and Singles Have Similar Planet and Stellar Properties Indicating a Common Origin
• The multiplicity distribution of Kepler's exoplanets
• On the patterns observed in Kepler multi-planet systems
• The Metallicity-Period-Mass Diagram of low-mass exoplanets
• Higher Compact Multiple Occurrence Around Metal-Poor M-Dwarfs and Late K-Dwarfs
• A Spectroscopic Analysis of the California-Kepler Survey Sample: II. Correlations of Stellar Metallicities with Planetary Architectures
• Evidence for a Non-Dichotomous Solution to the Kepler Dichotomy: Mutual Inclinations of Kepler Planetary Systems from Transit Duration Variations