A Tale of Two Circularization Periods

TL;DR

This study re-analyzes Kepler and TESS eclipsing binary data to empirically determine tidal circularization periods, revealing shorter periods than previously reported and highlighting differences in eccentricity distributions based on stellar age.

Contribution

It provides new empirical measurements of tidal circularization periods using eclipsing binary data, challenging prior estimates and emphasizing the importance of sample size and age in eccentricity studies.

Findings

Average circularization period is ~6 days.

Shorter circularization period of ~3 days for Kepler/TESS binaries.

Older binaries show different eccentricity distributions than younger ones.

Abstract

We re-analyze the pristine eclipsing binary data from the $\textit{Kepler}$ and TESS missions, focusing on eccentricity measurements at short orbital periods to emperically constrain tidal circularization. We find an average circularization period of $~$6 days, as well as a short circularization period of $\sim$3 days for the $\textit{Kepler}$/TESS field binaries. We argue previous spectroscopic binary surveys reported longer circularization periods due to small sample sizes, which were contaminated by an abundance of binaries with circular orbits out to $\sim$10 days, but we re-affirm their data shows a difference between the eccentricity distributions of young ($<$1 Gyr) and old ($>$3 Gyr) binaries. Our work calls into question the long circularization periods quoted often in the literature.