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A Tidal Origin for a Three-body Resonance in Kepler-221

Goldberg, Max and Batygin, Konstantin (2021) A Tidal Origin for a Three-body Resonance in Kepler-221. Astronomical Journal, 162 (1). Art. No. 16. ISSN 0004-6256. doi:10.3847/1538-3881/abfb78.

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Over the course of the last two decades, traditional models of planet formation have been repeatedly challenged by the emerging census of extrasolar planets. Key among them is the orbital architecture problem: while standard models of orbital migration predict resonant orbits for short-period objects, most planets do not appear to lie in orbital resonances. Here, we show that the four-planet system Kepler-221, not previously recognized to have active orbital resonances, has a three-body commensurability relation unique within the Kepler sample. Using a suite of numerical experiments as well as a perturbative analysis, we demonstrate that this system likely began as a resonant chain and proceeded to undergo large-scale divergence away from resonance, under the action of tidal dissipation. Our results further indicate that obliquity tides, driven by a secular spin–orbit resonance and mutual inclination, are an excellent candidate for driving this orbital divergence, and that the high tidal luminosity may also explain the anomalous size of planet b, which lies within the Fulton radius gap.

Item Type:Article
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URLURL TypeDescription Paper
Goldberg, Max0000-0003-3868-3663
Batygin, Konstantin0000-0002-7094-7908
Alternate Title:A Tidal Origin for a 3-body Resonance in Kepler-221
Additional Information:© 2021. The American Astronomical Society. Received 2020 December 11; revised 2021 April 20; accepted 2021 April 22; published 2021 June 15. We would like to thank Andrew Howard, Juliette Becker, and Daniel Fabrycky for illuminating discussions. This investigation was started as a project for a course in Exoplanet Dynamics at the University of Chicago. K.B. is grateful to the David and Lucile Packard Foundation and the Alfred P. Sloan Foundation for their generous support.
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:Exoplanet dynamics; Exoplanet tides; Exoplanet evolution; Orbital resonances
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet dynamics (490); Exoplanet tides (497); Exoplanet evolution (491); Orbital resonances (1181)
Record Number:CaltechAUTHORS:20210526-152357337
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Official Citation:Max Goldberg and Konstantin Batygin 2021 AJ 162 16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109263
Deposited By: George Porter
Deposited On:26 May 2021 22:46
Last Modified:16 Nov 2021 19:35

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