Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks
When a hot Jupiter orbits a star whose effective temperature exceeds ∼6100 K, its orbit normal tends to be misaligned with the stellar spin axis. Cooler stars typically have smaller obliquities, which may have been damped by hot Jupiters in resonance lock with axisymmetric stellar gravity modes (azi...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adc114 |
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| author | J. J. Zanazzi Eugene Chiang |
| author_facet | J. J. Zanazzi Eugene Chiang |
| author_sort | J. J. Zanazzi |
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| description | When a hot Jupiter orbits a star whose effective temperature exceeds ∼6100 K, its orbit normal tends to be misaligned with the stellar spin axis. Cooler stars typically have smaller obliquities, which may have been damped by hot Jupiters in resonance lock with axisymmetric stellar gravity modes (azimuthal number m = 0). Here we allow for resonance locks with nonaxisymmetric modes, which affect both stellar obliquity and spin frequency. Obliquities damp for all modes (−2 ≤ m ≤ 2). Stars spin-up for m > 0, and spin-down for m < 0. We carry out a population synthesis that assumes hot Jupiters form misaligned around both cool and hot stars, and subsequently lock onto modes whose m- values yield the highest mode energies for given starting obliquities. Core hydrogen burning enables hot Jupiters to torque low-mass stars, but not high-mass stars, into spin–orbit alignment. Resonance locking plus stellar spin-down from magnetic braking largely reproduces observed obliquities and stellar rotation rates and how they trend with stellar effective temperature and orbital separation. The possible suppression of resonance locking by nonlinear dissipation of gravity waves remains an outstanding issue. |
| format | Article |
| id | doaj-art-9eae4d72ef06461891c7ea498247cb46 |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-9eae4d72ef06461891c7ea498247cb462025-08-20T02:13:19ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01983215710.3847/1538-4357/adc114Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance LocksJ. J. Zanazzi0https://orcid.org/0000-0002-9849-5886Eugene Chiang1https://orcid.org/0000-0002-6246-2310Astronomy Department, Theoretical Astrophysics Center, and Center for Integrative Planetary Science, University of California, Berkeley, Berkeley, CA 94720, USA ; jzanazzi@berkeley.eduAstronomy Department, Theoretical Astrophysics Center, and Center for Integrative Planetary Science, University of California, Berkeley, Berkeley, CA 94720, USA ; jzanazzi@berkeley.edu; Department of Earth and Planetary Science, University of California , Berkeley, CA 94720, USAWhen a hot Jupiter orbits a star whose effective temperature exceeds ∼6100 K, its orbit normal tends to be misaligned with the stellar spin axis. Cooler stars typically have smaller obliquities, which may have been damped by hot Jupiters in resonance lock with axisymmetric stellar gravity modes (azimuthal number m = 0). Here we allow for resonance locks with nonaxisymmetric modes, which affect both stellar obliquity and spin frequency. Obliquities damp for all modes (−2 ≤ m ≤ 2). Stars spin-up for m > 0, and spin-down for m < 0. We carry out a population synthesis that assumes hot Jupiters form misaligned around both cool and hot stars, and subsequently lock onto modes whose m- values yield the highest mode energies for given starting obliquities. Core hydrogen burning enables hot Jupiters to torque low-mass stars, but not high-mass stars, into spin–orbit alignment. Resonance locking plus stellar spin-down from magnetic braking largely reproduces observed obliquities and stellar rotation rates and how they trend with stellar effective temperature and orbital separation. The possible suppression of resonance locking by nonlinear dissipation of gravity waves remains an outstanding issue.https://doi.org/10.3847/1538-4357/adc114Hot JupitersStar-planet interactionsTidal interactionStellar evolutionExoplanet formation |
| spellingShingle | J. J. Zanazzi Eugene Chiang Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks The Astrophysical Journal Hot Jupiters Star-planet interactions Tidal interaction Stellar evolution Exoplanet formation |
| title | Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks |
| title_full | Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks |
| title_fullStr | Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks |
| title_full_unstemmed | Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks |
| title_short | Spin and Obliquity Evolution of Hot Jupiter Hosts from Resonance Locks |
| title_sort | spin and obliquity evolution of hot jupiter hosts from resonance locks |
| topic | Hot Jupiters Star-planet interactions Tidal interaction Stellar evolution Exoplanet formation |
| url | https://doi.org/10.3847/1538-4357/adc114 |
| work_keys_str_mv | AT jjzanazzi spinandobliquityevolutionofhotjupiterhostsfromresonancelocks AT eugenechiang spinandobliquityevolutionofhotjupiterhostsfromresonancelocks |