The coevolution of migrating planets and their pulsating stars through episodic resonance locking

Abstract

Hot Jupiters are expected to form far from their host star and move to a close-in, circular orbit through a smooth, monotonic decay due to mild and constant tidal dissipation. Yet, systems exhibiting planet-induced stellar pulsations have recently been found, suggesting unexpectedly strong tidal interactions. Here we combine stellar evolution and tide models to show that dynamical tides raised by eccentric gas giants can excite chains of resonance locks with several modes, which enriches the dynamics seen in single-mode resonance locking of circularized systems. These series of resonance locks yield orders of magnitude larger changes in eccentricity and harmonic pulsations relative to those expected from a single episode of resonance locking or non-resonant tidal interactions. Resonances become more frequent as a star evolves off the main sequence, which provides an alternative explanation for the origin of some stellar pulsators and leads to the concept of ‘dormant migrating giants’. Evolution trajectories are characterized by competing episodes of inward and outward migration and the spin-up or spin-down of the star, which are sensitive to the system parameters. This is a new challenge in modelling migration paths and in contextualizing the observed populations of giant exoplanets and stellar binaries. This sensitivity, however, offers a new window for constraining the stellar properties of planetary hosts through tidal asteroseismology. A state-of-the-art model for planet–star interactions shows that migrating planets may coevolve with their pulsating stars through episodic resonances that drive substantial orbital migration and produce detectable tidal oscillations.