Tides in Stars and Planets

Resonance Locking in hot Jupiter Systems

Hot Jupiters around cool stars (below the Kraft break) have low stellar obliquities, while those around hot stars (above the Kraft break) have high obliquities.  It has long been postulated the different internal structures of cool vs. hot stars causes tidal dissipation to more efficiently damp the obliquities of cool stars.  Prof. Eugene Chiang and I examined how gravity mode resonances prolonged by stellar evolution can damp the obliquities of cool and hot stars hosting hot Jupiters.  We showed this process, known as resonance locking, preferentially damps the obliquities of cool stars due to the contraction of their stably stratified cores.

Resonance Locking in Stellar Binaries

Stellar binaries have long been known to have low eccentricities at short orbital periods, even when the binary is quite young, thought to be a relic of efficient tidal circularization during the star's pre-main sequence evolution.  Prof. Yanqin Wu and I examined how gravity mode resonances prolonged by stellar evolution can efficiently circularize stellar binaries during their pre-main sequence evolution.  We showed this process, known as resonance locking, circularizes binaries out to ~3-5 day orbital periods.  I later combined eclipsing and spectroscopic binary data to show this prediction agrees with the short-period binary eccentricity distribution.

Tides in Rocky Exoplanets

I have also dabbled briefly in tidal processes applied to the geophyiscs of rocky exoplanets, looking at processes which stress a rocky planet's lithosphere, which impact explanetary habitability.  With Prof. Dong Lai, I calculated the maximum triaxiality a rocky planet can sustain.  I showed the largest possible triaxiality for most rocky exoplanets is sufficiently large to resist the tidal torque working to synchronize the planet's spin, and capture a (short-period) planet into a spin-orbit resonance.  With Dr. Amaury Triaud, I showed tidal stresses acting on short-period exoplanets can weaken the planet's lithosphere, making plate tectonics more likely.


J. J. Zanazzi, Janosz Dewberry, & Eugene Chiang, 2024, ApJL, submitted.  PDF

J. J. Zanazzi, A Tale of Two Circularization Periods, 2022,  ApJL, 929, L27.  PDF 

J. J. Zanazzi & Yanqin Wu, Orbital Circularization of Binaries from Resonance Locking I: The Importance of the Pre-Main-Sequence.  2021, accepted to ApJ.  PDF 

J. J. Zanazzi & Amaury Triaud; The Ability of Significant Tidal Stress to Initiate Plate Tectonics. 2019, Icarus, 325, 55.  PDF

J. J. Zanazzi & Dong Lai; Triaxial Deformation and Asynchronous Rotation of Rocky Planets in the Habitable Zone of Low-Mass Stars.  2017, MNRAS, 469, 2879.  PDF