Absence of a metallicity effect for ultra-short-period planets

Abstract

Ultra-short-period (USP) planets are a newly recognized class of planets with periods shorter than one day and radii smaller than about 2 Earth radii. It has been proposed that USP planets are the solid cores of hot Jupiters that lost their gaseous envelopes due to photo-evaporation or Roche lobe overflow. We test this hypothesis by asking whether USP planets are associated with metal-rich stars, as has long been observed for hot Jupiters. We find the metallicity distributions of USP-planet and hot-Jupiter hosts to be significantly different ($p=3\times 10^{-4}$), based on Keck spectroscopy of Kepler stars. Evidently, the sample of USP planets is not dominated by the evaporated cores of hot Jupiters. The metallicity distribution of stars with USP planets is indistinguishable from that of stars with short-period planets with sizes between 2--4~$R_{\oplus }$. Thus it remains possible that the USP planets are the solid cores of formerly gaseous planets smaller than Neptune.

AJ, in press

References in corpus (23)

• The Transiting Exoplanet Survey Satellite
• The Dartmouth Stellar Evolution Database
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Most 1.6 Earth-Radius Planets are not Rocky
• Atmospheric Escape from Hot Jupiters
• KEPLER's First Rocky Planet: Kepler-10b
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• Three regimes of extrasolar planets inferred from host star metallicities
• The California-Kepler Survey. I. High Resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets
• A Study of the Shortest-Period Planets Found With Kepler
• The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
• Magnetospheric Truncation, Tidal Inspiral, and the Creation of Short and Ultra-Short Period Planets
• Exploring the alpha-enhancement of metal-poor planet-hosting stars. The Kepler and HARPS samples
• A Super-Solar Metallicity For Stars With Hot Rocky Exoplanets
• Detection of Stars within $\sim$0.8 arcseconds of Kepler Objects of Interest
• From Hot Jupiters to Super-Earths via Roche Lobe Overflow
• Two Small Planets Transiting HD 3167
• A New Model of Roche-lobe Overflow for Short-Period Gaseous Planets and Binary Stars
• The metallicity distribution and hot Jupiter rate of the Kepler field: Hectochelle High-resolution spectroscopy for 776 Kepler target stars
• A Continuum of Planet Formation Between 1 and 4 Earth Radii
• A population of planetary systems characterized by short-period, Earth-sized planets
• On the formation of the Kepler-10 planetary system
• Ultra Short Period Planets in K2 with companions: a double transiting system for EPIC 220674823

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• Origins of Hot Jupiters
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• An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141
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• Metallicity-Dependent Signatures in the Kepler Planets
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• The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b
• Do Metal-Rich Stars Make Metal-Rich Planets? New Insights on Giant Planet Formation from Host Star Abundances
• A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period Planet
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• K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf
• TOI-2076 and TOI-1807: Two young, comoving planetary systems within 50 pc identified by TESS that are ideal candidates for further follow-up
• Mass determinations of the three mini-Neptunes transiting TOI-125
• TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
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• AutoRegressive Planet Search: Application to the Kepler Mission
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• An ultra-short period rocky super-Earth orbiting the G2-star HD 80653
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• Exoplanet Populations and their Dependence on Host Star Properties
• Elemental Abundances of the Super-Neptune WASP-107b's Host Star Using High-resolution, Near-infrared Spectroscopy
• HD 20329b: An ultra-short-period planet around a solar-type star found by TESS
• On the origin of dynamically isolated hot Earths
• Dust Accumulation near the Magnetospheric Truncation of Protoplanetary Discs around T Tauri Stars
• Probing Kepler's hottest small planets via homogeneous search and analysis of optical secondary eclipses and phase variations
• No Metallicity Correlation Associated with the Kepler Dichotomy
• Survival Function Analysis of Planet Size Distribution with GAIA Data Release 2 Updates
• A Reanalysis of the Composition of K2-106b: an Ultra-short Period Super-Mercury Candidate
• The Period Distribution of Hot Jupiters is Not Dependent on Host Star Metallicity
• CHEOPS and TESS view of the ultra-short period super-Earth TOI-561 b
• TOI-1442 b and TOI-2445 b: two potentially rocky ultra-short period planets around M dwarfs
• Planets Across Space and Time (PAST). VI. Age Dependence of the Occurrence and Architecture of Ultra-Short-Period Planet Systems
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• The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys
• Two neighbours of the ultra-short-period Earth-sized planet K2-157 b in the warm Neptunian savanna
• Two Bright M Dwarfs Hosting Ultra-Short-Period Super-Earths with Earth-like Compositions
• Radius and mass distribution of ultra-short period planets
• The role of inner disk edges in shaping ultra-short-period planet systems around late M dwarfs