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

School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel

^★ Corresponding author: eyalhadad@mail.tau.ac.il

Received: 18 May 2025
Accepted: 16 July 2025

Abstract

The Gaia DR3 catalogue includes line-broadening measurements (vbroad) for 10 387 eclipsing binaries. In this study, we focus on a subset of 977 short-period main-sequence sources with primary radii in the range of [1.25, 3] R_⊙, effective temperatures between 5600 and 8000 K, orbital periods from 0.3 to 3 days, vbroad measurements between 30 and 300 km/s, eclipse depth ratios below 0.7 and |e cos ω| < 0.1. Our analysis reveals a clear inverse correlation between the derived vbroad values and the orbital periods of these systems, consistent with tidal synchronisation and spin–orbit alignment. We further compare the Gaia vbroad results with the expected rotational velocities of the primaries of these binaries, given the radius estimate of these stars. We find that the vbroad measurements are generally consistent with the expected rotational broadening, except for a systematic lower factor of approximately 10%.