Detailed Characterization of Heartbeat Stars and their Tidally Excited Oscillations

TL;DR

This study analyzes heartbeat stars using Kepler data to characterize tidally excited oscillations, revealing potential resonance locking in one system and enhancing understanding of tidal interactions in eccentric binaries.

Contribution

It provides detailed modeling and frequency analysis of tidally excited oscillations in specific heartbeat stars, exploring resonance locking mechanisms.

Findings

Resonance locking likely in KIC 11494130

No resonance locking in KIC 6117415 or KIC 5790807

Improved understanding of tidal excitation in eccentric binaries

Abstract

Heartbeat stars are a class of eccentric binary stars with short-period orbits and characteristic "heartbeat" signals in their light curves at periastron, caused primarily by tidal distortion. In many heartbeat stars, tidally excited oscillations can be observed throughout the orbit, with frequencies at exact integer multiples of the orbital frequency. Here, we characterize the tidally excited oscillations in the heartbeat stars KIC 6117415, KIC 11494130, and KIC 5790807. Using Kepler light curves and radial velocity measurements, we first model the heartbeat stars using the binary modeling software ELLC, including gravity darkening, limb darkening, Doppler boosting, and reflection. We then conduct a frequency analysis to determine the amplitudes and frequencies of the tidally excited oscillations. Finally, we apply tidal theories to stellar structure models of each system to determine whether chance resonances can be responsible for the observed tidally excited oscillations, or whether a resonance locking process is at work. We find that resonance locking is likely occurring in KIC 11494130, but not in KIC 6117415 or KIC 5790807.