Small Planets in the Galactic Context: Host Star Kinematics, Iron, and $\alpha$ Element Enhancement

Abstract

We explored the occurrence rate of small close-in planets among $\text{Kepler}$ target stars as a function of the iron abundance and the stellar total velocity $V_{\mathrm{tot}}$. We estimated the occurrence rate of those planets by combining information from LAMOST and the California-$\text{Kepler}$ Survey (CKS) and found that iron-poor stars exhibit an increase in the occurrence with $V_{\mathrm{tot}}$ from $f<0.2$ planets per star at $V_{\mathrm{tot}}<30{\mathrm{km}\mathrm{s}}^{-1}$ to $f\sim 1.2$ at $V_{\mathrm{tot}}>90{\mathrm{km}\mathrm{s}}^{-1}$. We suggest this planetary profusion may be a result of a higher abundance of $\alpha$ elements associated with iron-poor, high-velocity stars. Furthermore, we have identified an increase in small planet occurrence with iron abundance, particularly for the slower stars ($V_{\mathrm{tot}}<30{\mathrm{km}\mathrm{s}}^{-1}$), where the occurrence increased to $f\sim 1.1$ planets per star in the iron-rich domain. Our results suggest there are two regions in the $([\mathrm{Fe}/\mathrm{H}],[\alpha /\mathrm{Fe}])$ plane in which stars tend to form and maintain small planets. We argue that analysis of the effect of overall metal content on planet occurrence is incomplete without including information on both iron and $\alpha$ element enhancement.

arXiv comment8 pages, 4 figures, accepted for publication in AJ

References in corpus (36)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Transiting Exoplanet Survey Satellite
• Gaia Data Release 2: The astrometric solution
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The PLATO 2.0 Mission
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• Spectroscopic [Fe/H] for 98 extra-solar planet-host stars: Exploring the probability of planet formation
• Kepler Input Catalog: Photometric Calibration and Stellar Classification
• The Chemical Compositions of Galactic Disk F and G Dwarfs
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• The GALAH Survey: Second Data Release
• Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets
• The California-Kepler Survey. I. High Resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets
• Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
• Exoplanet population inference and the abundance of Earth analogs from noisy, incomplete catalogs
• The Exoplanet Census: A General Method, Applied to Kepler
• Deep learning of multi-element abundances from high-resolution spectroscopic data
• Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest
• Label Transfer from APOGEE to LAMOST: Precise Stellar Parameters for 450,000 LAMOST Giants
• Exploring the alpha-enhancement of metal-poor planet-hosting stars. The Kepler and HARPS samples
• Estimating stellar atmospheric parameters, absolute magnitudes and elemental abundances from the LAMOST spectra with Kernel-based Principal Component Analysis
• Constraining planet structure and composition from stellar chemistry: trends in different stellar populations
• Heavy metal rules. I. Exoplanet incidence and metallicity
• On the correlation between metallicity and the presence of giant planets
• A Comparison of Stellar Elemental Abundance Techniques and Measurements
• The Gaia-ESO Survey: Characterisation of the [alpha/Fe] sequences in the Milky Way discs
• Chemical Abundances of Main-Sequence, Turn-off, Subgiant and red giant Stars from APOGEE spectra I: Signatures of Diffusion in the Open Cluster M67
• LAMOST observations in the Kepler field. II. Database of the low-resolution spectra from the five-year regular survey
• Compact multi-planet systems are more common around metal poor hosts
• Exploring Kepler Giant Planets in the Habitable Zone
• Influence of Stellar Metallicity on Occurrence Rates of Planets and Planetary Systems
• The GALAH survey: properties of the Galactic disk(s) in the solar neighbourhood
• Chemical fingerprints of hot Jupiter planet formation
• LAMOST DR1: Stellar parameters and chemical abundances with SP_Ace
• The GAPS Programme with HARPS-N at TNG XVIII. Two new giant planets around the metal-poor stars HD 220197 and HD 233832

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• Ariel stellar characterisation: I -- homogeneous stellar parameters of 187 FGK planet host stars Description and validation of the method
• Occurrence rates of small planets from HARPS: Focus on the Galactic context
• How the origin of stars in the Galaxy impacts the composition of planetary building blocks
• Planet Occurrence Rate Correlated to Stellar Dynamical History: Evidence from Kepler and Gaia
• Exoplanets Across Galactic Stellar Populations with PLATO: Estimating Exoplanet Yields Around FGK Stars for the Thin Disk, Thick Disk and Stellar Halo
• Planetary mass-radius relations across the galaxy
• Populating The Milky Way: Characterising Planet Demographics by Combining Galaxy Formation Simulations and Planet Population Synthesis Models
• Searching For Transiting Planets Around Halo Stars. I. Sample Selection and Validation
• Chemical composition of planetary hosts: C, N, and $\alpha$-element abundances
• Elemental Abundances of Kepler Objects of Interest in APOGEE DR17
• Chemical composition of planetary hosts: II. Abundances of neutron-capture elements
• Quantifying chemical and kinematical properties of Galactic disks
• Stellar chemistry and planet size: insights from GALAH DR4