The influence of metallicity on a combined stellar and disk evolution

TL;DR

This paper presents a self-consistent model of stellar and disk evolution during the T Tauri phase, highlighting how metallicity influences disk heating, lifetime, and stellar spin, with implications for understanding early stellar development.

Contribution

It introduces a combined numerical model that couples hydrodynamic disk evolution with stellar spin and evolution, incorporating metallicity effects for the first time.

Findings

Low metallicity disks are heated differently and have shorter lifetimes.

Stars in low metallicity environments spin faster due to shorter disk lifetimes.

The model explains observed short disk lifetimes in low metallicity clusters.

Abstract

The effects of an accretion disk are crucial to understanding the evolution of young stars. During the combined evolution, stellar and disk parameters influence each other, motivating a combined stellar and disk model. This makes a combined numerical model, evolving the disk alongside the star, the next logical step in the progress of studying early stellar evolution. We aim to understand the effects of metallicity on the accretion disk and the stellar spin evolution during the T~Tauri phase. We combine the numerical treatment of a hydrodynamic disk with stellar evolution, including a stellar spin model, allowing a self-consistent calculation of the back-reactions between the individual components. We present the self-consistent theoretical evolution of T-Tauri stars coupled to a stellar disk. We find that disks in low metallicity environments are heated differently and have shorter lifetimes, compared to their solar metallicity counterparts. Differences in stellar radii, the contraction rate of the stellar radius, and the shorter disk lifetimes result in faster rotation of low metallicity stars. We present an additional explanation for the observed short disk lifetimes in low metallicity clusters. A combination of our model with previous studies (e.g., a metallicity-based photo-evaporation) could help to understand disk evolution and dispersal at different metallicities. Furthermore, the stellar spin evolution model includes several important effects, previously ignored (e.g., the stellar magnetic field strength and a realistic calculation of the disk lifetime) and we motivate to include our results as initial or input parameters for further spin evolution models, covering the stellar evolution towards and during the main sequence.