Mass-transfer properties of overcontact systems in the Kepler eclipsing binary catalog

TL;DR

This study investigates mass-transfer rates in overcontact binary systems from the Kepler catalog, revealing how these rates depend on various astrophysical parameters and differ from other binary types, with implications for binary evolution.

Contribution

It provides new insights into the dependence of mass-transfer rates on multiple parameters in overcontact systems, highlighting differences from semi-detached or detached binaries and considering subtype variations.

Findings

Mass-transfer rates correlate differently with astrophysical quantities in overcontact systems.

Rapid mass exchange occurs as evolution progresses, but this trend varies with period and mass.

Different correlations are observed between W- and A-type W UMa systems.

Abstract

We selected mass-transferring binary candidates from the catalog of Kepler eclipsing binary stars and investigated the dependence of the mass-transfer rate on several astrophysical quantities, including orbital period, semi-major axis, mass ratio, fill-out factor, temperature, and mass. We selected these candidates using $O-C$ diagrams and calculated their mass-transfer rates. Primary masses were obtained from the mass--temperature relation, and the temperatures of the component stars were extracted from a catalog of temperatures for Kepler eclipsing binary stars. The mass-transfer rates of overcontact systems have associations with astrophysical quantities that seem to differ from those of semi-detached or detached systems. These associations indicate that mass exchange from more- to less-massive components (from less- to more-massive components) generally becomes rapid (slow) as the mass exchange evolves. However, for mass exchange from more- to less-massive components, this tendency is not reasonable for binaries with a short period ($P<0.4$ d) and low mass ($M_1<1.2$ M$_\odot$) because the correlations of these binaries are opposite to those of binaries with long period and high mass. These different correlations likely arise from differences in correlation between subtypes of W UMa systems (i.e., W- and A-types). Alternatively, when mass exchange from more- to less-massive components reoccurs after a mass-ratio reversal, its properties may differ from those of the first mass exchange.