Metallicity-dependent signatures in the Kepler planets

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Title: Metallicity-dependent signatures in the Kepler planets
Authors: Owen, JE
Murray-Clay, R
Item Type: Journal Article
Abstract: Using data from the California-Kepler Survey (CKS), we study trends in planetary properties with host star metallicity for close-in planets. By incorporating knowledge of the properties of the planetary radius gap identified by the CKS survey, we are able to investigate the properties of planetary cores and their gaseous envelopes separately. Our primary findings are that the solid core masses of planets are higher around higher metallicity stars and that these more massive cores were able to accrete larger gas envelopes. Furthermore, investigating the recently reported result that planets with radii in the range ( 2–6 R⊕) are more common at short periods around higher metallicity stars in detail, we find that the average host star metallicity of H/He atmosphere-hosting planets increases smoothly inside an orbital period of ∼20 d. We interpret the location of the metallicity increase within the context of atmospheric photoevaporation: higher metallicity stars are likely to host planets with higher atmospheric metallicity, which increases the cooling in the photoevaporative outflow, lowering the mass-loss rates. Therefore, planets with higher metallicity atmospheres are able to resist photoevaporation at shorter orbital periods. Finally, we find evidence at 2.8 σ that planets that do not host H/He atmospheres at long periods are more commonly found around lower metallicity stars. Such planets are difficult to explain by photoevaporative stripping of planets which originally accreted H/He atmospheres. Alternatively, this population of planets could be representative of planets that formed in a terrestrial-like fashion, after the gas disc dispersed.
Issue Date: 31-Oct-2018
Date of Acceptance: 17-Jul-2018
ISSN: 0035-8711
Publisher: Oxford University Press (OUP)
Start Page: 2206
End Page: 2216
Journal / Book Title: Monthly Notices of the Royal Astronomical Society
Volume: 480
Issue: 2
Copyright Statement: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Sponsor/Funder: The Royal Society
Funder's Grant Number: UF150412
Keywords: 0201 Astronomical And Space Sciences
Astronomy & Astrophysics
Publication Status: Published
Open Access location:
Online Publication Date: 2018-07-20
Appears in Collections:Physics
Faculty of Natural Sciences

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