Detailed equilibrium and dynamical tides: impact on circularization and synchronization in open clusters

Binary stars evolve into chemically-peculiar objects and are a major driver of the Galactic enrichment of heavy elements. During their evolution they undergo interactions, including tides, that circularize their orbits and synchronize stellar spins, impacting both individual systems and stellar populations. My recent work introduces an accurate implementation of equilibrium and dynamical tides in the stellar population code binary_c, relying on Zahn’s theory and purpose-built MESA model grids. I will first introduce the stellar population code itself, and the overhaul that we call MINT. We assess the impact of tides and initial orbital-parameter distributions on circularization and synchronization processes in a range of open clusters of ages 4Myr to 7Gyr. Studying the eccentricity-period diagram, we find that the initial distributions dominate the agreement with observations so that main-sequence tides hardly make a difference: this proves the common approach of constraining tidal-efficiency parameters using the e-logP distribution alone difficult or impossible. Instead, we find that the synchronization process carries a more striking signature of the tides, thus providing a measure of tidal efficiency that is verifiable. Combined measurements of orbital parameters and stellar spins could crucially lead to better tide, magnetic braking and initial rotation rate prescriptions. The use of MESA grids and Zahn tides also has implications on metal-free stars, that are created in the very early Universe. In two separate works, we assessed the impact of the primordial initial mass function on observable signatures such as the 21-cm signal and their X-ray emission. These are only the first examples of the cornucopia of science that improving stellar parameters and tidal prescriptions in population codes can provide in the future.

14/06/2022 - 12:30
Dr. Giovanni Mirouh
Univ. Granada