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The distribution of mutual inclinations arising from the stellar quadrupole moment

Schultz, Kathleen and Spalding, Christopher and Batygin, Konstantin (2021) The distribution of mutual inclinations arising from the stellar quadrupole moment. Monthly Notices of the Royal Astronomical Society, 506 (2). pp. 2999-3009. ISSN 0035-8711. doi:10.1093/mnras/stab1899.

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A large proportion of transiting planetary systems appear to possess only a single planet as opposed to multiple transiting planets. This excess of singles is indicative of significant mutual inclinations existing within a large number of planetary systems, but the origin of these misalignments is unclear. Moreover, recent observational characterization reveals that mutual inclinations tend to increase with proximity to the host star. These trends are both consistent with the dynamical influence of a strong quadrupolar potential arising from the host star during its early phase of rapid rotation, coupled with a non-zero stellar obliquity. Here, we simulate a population of planetary systems subject to the secular perturbation arising from a tilted, oblate host star as it contracts and spins down subsequent to planet formation. We demonstrate that this mechanism can reproduce the general increase in planet-planet mutual inclinations with proximity to the host star, and delineate a parameter space wherein the host star can drive dynamical instabilities. We suggest that approximately 5–10 per cent of low-mass Kepler systems are susceptible to this instability mechanism, suggesting that a significant number of single-transiting planets may truly be intrinsically single. We also report a novel connection between instability and stellar obliquity reduction and make predictions that can be tested within upcoming TESS observations.

Item Type:Article
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URLURL TypeDescription Paper
Schultz, Kathleen0000-0002-2821-4612
Spalding, Christopher0000-0001-9052-3400
Batygin, Konstantin0000-0002-7094-7908
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 June 30. Received 2021 June 30; in original form 2020 October 30. Published: 05 July 2021. The authors would like to thank Neil Comins and Fei Dai for enlightening discussions. KS additionally thanks the Advanced Computing Group at the University of Maine for use of their facilities. CS is grateful for the generous support of the Heising-Simons Foundation. Data Availability: The data underlying this paper will be shared on reasonable request to the corresponding author.
Funding AgencyGrant Number
Heising-Simons Foundation51 Pegasi b Fellowship
Subject Keywords:planets and satellites: dynamical evolution and stability – planets and satellites: formation – planet–star interactions – stars: rotation
Issue or Number:2
Record Number:CaltechAUTHORS:20211013-154750606
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Official Citation:Kathleen Schultz, Christopher Spalding, Konstantin Batygin, The distribution of mutual inclinations arising from the stellar quadrupole moment, Monthly Notices of the Royal Astronomical Society, Volume 506, Issue 2, September 2021, Pages 2999–3009,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111398
Deposited By: Tony Diaz
Deposited On:13 Oct 2021 16:01
Last Modified:13 Oct 2021 16:01

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