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Tidal Circularization of Binaries by Resonance Locking

Presentation #204.04 in the session “Evolution of Stellar Multiples”.

Published onJun 01, 2021
Tidal Circularization of Binaries by Resonance Locking

Although tidal dissipation in binary stars has been studied for over a century, theoretical predictions have yet to match the observed properties of binary populations. In the first part of this talk, we quantitatively examine the efficacy of resonance locking in stellar binaries, where tidal dissipation arises from resonances between the star’s natural oscillation frequencies (from gravity modes) and harmonics of the orbital frequency, ‘locked’ for an extended period of time due to concurrent stellar evolution. We find resonance locking occurs primarily during the pre-main-sequence, and can circularize binaries interior to ~4 days, although non-linear effects may modify this result. In the second part of this talk, we compare the predictions of resonance locking with binary eccentricity measurements from the Sloan Digital Sky Survey and Kepler missions. After introducing statistical methods to constrain the presence of multiple eccentricity distributions, we find the presence of a nearly-circular population which extends to orbital periods of ~10 days, and an eccentric population with binaries having circular orbits interior to only ~4 days. Resonance locking onto linear modes is consistent with the properties of the latter population, even after varying the primary spectral type, binary effective temperature, and binary age. Our results usher in a new age for ‘precision’ tidal theories, by matching the detailed predictions of tidal theories based on self-consistent physics, with the statistical properties of orbits in different astrophysical systems.

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