2022ApJ...929L..27Z

We reanalyze the exquisite eclipsing binary data from the Kepler and TESS missions, focusing on eccentricity measurements at short orbital periods to empirically constrain tidal circularization. We calculate a circularization period of ∼6 days due to nearly circular binaries with long orbital periods ("cold core") but find many binaries with moderate eccentricities that circularize interior to only ∼3 days ("eccentricity envelope"). We show that these features are present in previous spectroscopic surveys. We also reaffirm the statistically significant difference between the eccentricity distributions of young (<1 Gyr) and old (>3 Gyr) binaries. Our work introduces new methods that have the potential to reconcile theoretical predictions with observations to empirically constrain tidal circularization.