Kepler-167e as a Probe of the Formation Histories of Cold Giants with Inner Super-Earths

February 2022 • 2022ApJ...926...62C

Authors • Chachan, Yayaati • Dalba, Paul A. • Knutson, Heather A. • Fulton, Benjamin J. • Thorngren, Daniel • Beichman, Charles • Ciardi, David R. • Howard, Andrew W. • Van Zandt, Judah

Abstract • The observed correlation between outer giant planets and inner super-Earths is emerging as an important constraint on planet formation theories. In this study, we focus on Kepler-167, which is currently the only system known to contain both inner transiting super-Earths and a confirmed outer transiting gas giant companion beyond 1 au. Using long-term radial velocity monitoring, we measure the mass of the gas giant Kepler-167e (P = 1071 days) to be ?{1.01}_{-0.15}^{+0.16}$ M _J, thus confirming it as a Jupiter analog. We refit the Kepler photometry to obtain updated radii for all four planets. Using a planetary structure model, we estimate that Kepler-167e contains 66 ± 19 M _⊕ of solids and is significantly enriched in metals relative to its solar-metallicity host star. We use these new constraints to explore the broader question of how systems like Kepler-167 form in the pebble accretion framework for giant planet core formation. We utilize simple disk evolution models to demonstrate that more massive and metal-rich disks, which are the most favorable sites for giant planet formation, can also deliver enough solids to the inner disk to form systems of super-Earths. We use these same models to constrain the nature of Kepler-167's protoplanetary disk and find that it likely contained ≳300 M _⊕ of dust and was ≳40 au in size. These values overlap with the upper end of the observed dust mass and size distributions of Class 0 and I disks and are also consistent with the observed occurrence rate of Jupiter analogs around Sun-like stars.

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IPAC Authors
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David Ciardi

Senior Scientist

Benjamin Fulton

Assistant Scientist