Tidal Synchronization of TESS Eclipsing Binaries

Abstract Tidal synchronization plays a fundamental role in the evolution of binary star systems. However, key details such as the timescale of synchronization, efficiency of tidal dissipation, rotation period, and dependence on stellar mass are not well constrained. We present a catalog of rotation periods, orbital periods, and eccentricities from eclipsing binaries (EBs) that can be used to study the role of tides in the rotational evolution of low-mass dwarf (FGKM spectral type) binaries. This study presents the largest catalog of EB orbital and rotational periods ( P orb and P rot ) measured from the Transiting Exoplanet Satellite Survey (TESS). We first classify 4584 light curves from the TESS EB catalog according to out-of-eclipse stellar variability type: starspot modulation, ellipsoidal variability, nonperiodic variability, and “other” variability (e.g., pulsations). We then manually validate each light curve’s classification, resulting in a sample of 1039 candidates with 584 high-confidence EBs that exhibit detectable starspot modulation. From there, we measure and compare the rotation period of each starspot-modulated EB using three methods: a Lomb–Scargle periodogram, autocorrelation function, and phase dispersion minimization. We find that our period distributions are consistent with previous work that used a sample of 816 starspot EBs from Kepler to identify two populations: a synchronous population (with P orb ≈ P rot ), and a subsynchronous population (with 8 P orb ≈ 7 P rot ). Using Bayesian model comparison, we find that a bimodal distribution is a significantly better fit than a unimodal distribution for the Kepler and TESS samples, both individually or combined, confirming that the subsynchronous population is statistically significant.