Evidence for synchronisation of Gaia eclipsing binaries from their stellar rotational velocity

Abstract

The Gaia DR3 catalogue includes line-broadening (vbroad) measurements for 10,387 eclipsing binaries. In this study, we focus on a subset of 977 short-period main-sequence systems with primary radii between 1.25 and 3 solar radii, effective temperatures from 5600 to 8000 K, orbital periods between 0.3 and 3 days, vbroad values from 30 to 300 km/s, eclipse depth ratios below 0.7, and eccentricity indicators |e cos(omega)| less than 0.1. We find a clear inverse correlation between vbroad and orbital period, consistent with tidal synchronisation and spin-orbit alignment. Comparing the Gaia vbroad values with the expected rotational velocities based on stellar radii, we find that the measurements are generally consistent with rotational broadening, albeit with a systematic offset of approximately 10 percent.