Tidal Dissipation in Stars 

Resonance Locking in hot Jupiter Systems

Hot Jupiters around cool stars have low stellar obliquities, while those around hot stars have high obliquities.  It has long been postulated thick convective envelopes of cool stars cause efficient tidal dissipation, aligning the stellar spin with the planet's orbit normal, but the proposed tidal theories suffer difficulties (see e.g. Albrecht+ 2022).  I examined how gravity mode resonances prolonged by stellar evolution ('resonance locking') preferentially damp the obliquities of cool stars hosting hot Jupiters, due to the contraction of their radiative 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.  I examined how resonance locks onto gravity modes can efficiently circularize stellar binaries out to ~3-5 day orbital periods during their pre-main sequence evolution.  I later showed this prediction agrees with what I called the 'eccentric envelope' seen in the demographics of eclipsing and spectroscopic binaries.

Circumbinary Planets Hidden by Circularization

Although over a dozen planets orbiting binaries (circumbinary planets) have been detected as they transit the binary's orbital plane, none have been detected around binaries with orbital periods less than ~7 days.  Interestingly, this is close to the period most binaries have circular orbits, due to tidal circularization (e.g. Zanazzi 2022).  With Saahit Mogan, we showed tidal circularization leaves circumbinary planets stranded at large separations, making them more difficult to detect.

Publications

Saahit Mogan, J. J. Zanazzi, & Eugene Chiang; Concealing Circumbinary Planets with Tidal Shrinkage, subm. to ApJ, arXiv:2412.01616. PDF 

J. J. Zanazzi & Eugene Chiang; Spin and Obliquity Evolution of Hot Jupiter Hosts during Resonance Locks, subm. to ApJ, arXiv:2410.10943. PDF 

Knudstrup E., Albrecht S., Winn J., Gandolfi D., Zanazzi J. J., et al.; Obliquities of exoplanet host stars: Nineteen new and updated measurements, and trends in the sample of 205 measurements. 2024, A&A, 690, A379.  PDF 

Giacalone S., Dai F., Zanazzi J. J., et al.; The OATMEAL Survey. I. Low Stellar Obliquity in the Transiting Brown Dwarf System GPX-1. 2024, AJ, 168, 189. PDF 

J. J. Zanazzi, Janosz Dewberry, & Eugene Chiang, Damping Obliquities of Hot Jupiter Hosts by Resonance Locking, 2021, ApJL, 967, L29.  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, AJ, 161, 263. PDF