Orbital and physical parameters of eclipsing binaries from the Optical Gravitational Lensing Experiment catalogue: testing the tidal circularization

Abstract

ABSTRACT Tidal forces are an important process in the pre-main-sequence phase (as reported by Zahn and Bouchet in their now well-known paper) and throughout the main-sequence phase of stellar evolution. Nevertheless, uncertainty over tidal forces affects estimates obtained from models of the circularization and synchronization of the orbit by tidal interactions. Here, we search for evidence of tidal circularization in close binaries using a large sample of well-characterized eclipsing systems. We searched Optical Gravitational Lensing Experiment (OGLE) photometric catalogue for the Southern hemisphere from the Southern hemisphere for eclipsing binaries in eccentric orbits. We present precise values of the eccentricity and orbital and stellar parameters of eight detached, eclipsing stars from the OGLE catalogue that were determined by jointly modelling light curves and spectral analysis. The temperatures and relative radii of their components, as well as their mass ratios, were also calculated with high accuracy. We find a clear dependence of the components' relative radii and orbital period on the eccentricity. The determination of eccentricities as a function of period potentially allows us to infer the role of tidal circularization. The (P, r1,2) distribution of the known eccentric binaries exhibits a rough trend of increasing eccentricity with period. This suggests that the secondary components in binaries with longer orbital periods may be tidally circularized significantly more efficiently than is usually assumed. Observing this effect is challenging because it requires large and well-characterized samples that include many types of systems. Here we seek evidence of the predicted dependence of circularization on the relative radii using a sample of eclipsing binaries observed by OGLE.