Rediscussion of eclipsing binaries. Paper XII. The F-type twin system ZZ Bo\"otis

TL;DR

This study precisely characterizes the physical properties of the F-type eclipsing binary ZZ Boo using TESS light curves and radial velocities, clarifying component identities and evolutionary status with high accuracy.

Contribution

First detailed identification of primary and secondary stars in ZZ Boo using high-quality TESS data and radial velocities, resolving past confusion.

Findings

Primary star is hotter but smaller and less massive.

Secondary star is more evolved and larger.

Good agreement with theoretical models at 1.7 Gyr.

Abstract

ZZ Boo is an F-type detached eclipsing binary system containing two almost-identical stars on a circular orbit with a period of 4.992 d. We analyse light curves from two sectors of observations with the Transiting Exoplanet Survey Satellite (TESS) and two published sets of radial velocities of the component stars to determine their physical properties to high precision. We find masses of 1.558 +/- 0.008 Msun and 1.599 +/- 0.012 Msun, and radii of 2.063 +/- 0.006 Rsun and 2.205 +/- 0.006 Rsun. The similarity in the primary and secondary eclipse depths has led to confusion in the past. The high quality of the TESS data means we can, for the first time, clearly identify which is which. The primary star is conclusively hotter but smaller and less massive than the secondary star. We define a new high-precision orbital ephemeris and obtain effective temperatures using the Gaia parallax of the system. The secondary star is more evolved than the primary and a good agreement with theoretical predictions is found for a solar chemical composition and an age of 1.7 Gyr.