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Orbital Decay of Short-period Exoplanets via Tidal Resonance Locking

Ma, Linhao and Fuller, Jim (2021) Orbital Decay of Short-period Exoplanets via Tidal Resonance Locking. Astrophysical Journal, 918 (1). Art. No. 16. ISSN 0004-637X. doi:10.3847/1538-4357/ac088e.

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A large fraction of known exoplanets have short orbital periods where tidal excitation of gravity waves within the host star causes the planets' orbits to decay. We study the effects of tidal resonance locking, in which the planet locks into resonance with a tidally excited stellar gravity mode. Because a star's gravity mode frequencies typically increase as the star evolves, the planet's orbital frequency increases in lockstep, potentially causing much faster orbital decay than predicted by other tidal theories. Due to nonlinear mode damping, resonance locking in Sun-like stars likely only operates for low-mass planets (M ≲ 0.1 M_(Jup)), but in stars with convective cores it can likely operate for all planetary masses. The orbital decay timescale with resonance locking is typically comparable to the star's main-sequence lifetime, corresponding to a wide range in effective stellar quality factor (10³ ≲ Q' ≲ 10⁹), depending on the planet's mass and orbital period. We make predictions for several individual systems and examine the orbital evolution resulting from both resonance locking and nonlinear wave dissipation. Our models demonstrate how short-period massive planets can be quickly destroyed by nonlinear mode damping, while short-period low-mass planets can survive, even though they undergo substantial inward tidal migration via resonance locking.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ma, Linhao0000-0001-6117-5750
Fuller, Jim0000-0002-4544-0750
Additional Information:© 2021. The American Astronomical Society. Received 2021 March 22; revised 2021 May 18; accepted 2021 June 3; published 2021 August 30. We thank Hang Yu, Rich Townsend, and Josh Winn for very helpful discussion and feedback. This work is partially supported by NASA through grant 20-XRP20 2-0147. J.F. is thankful for support through an Innovator Grant from The Rose Hills Foundation, and the Sloan Foundation through grant FG-2018-10515. Software: MESA (Paxton et al. 2011, 2013, 2015, 2018, 2019), GYRE (Townsend & Teitler 2013; Townsend et al. 2018; Goldstein & Townsend 2020).
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
NASA20-XRP20 2-0147
Rose Hills FoundationUNSPECIFIED
Alfred P. Sloan FoundationFG-2018-10515
Subject Keywords:Exoplanets; Tidal interaction; Stellar oscillations; Stellar evolution
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanets (498); Tidal interaction (1699); Stellar oscillations (1617); Stellar evolution (1599)
Record Number:CaltechAUTHORS:20210526-152346612
Persistent URL:
Official Citation:Linhao Ma and Jim Fuller 2021 ApJ 918 16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109260
Deposited By: George Porter
Deposited On:26 May 2021 22:56
Last Modified:31 Aug 2021 20:33

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