The influence of metallicity on a combined stellar and disk evolution

Abstract

Context. Determining the effects of an accretion disk is crucial to understanding the evolution of young stars. During the combined evolution, stellar and disk parameters influence one another, which motivated us to develop a combined stellar and disk model. This makes a combined numerical model, with the disk evolving alongside the star, the next logical step in the progress of studying early stellar evolution. Aims. We aim to understand the effects of metallicity on the accretion disk and the stellar spin evolution during the T Tauri phase. Methods. We combined the numerical treatment of a hydrodynamic disk with stellar evolution, including a stellar spin model and allowing a self-consistent calculation of the back-reactions between the individual components. Results. 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 low-metallicity stars rotating more rapidly. Conclusions. We present an additional explanation for the observed short disk lifetimes in low-metallicity clusters. A combination of our model with those of previous studies (e.g., a metallicity-based photo-evaporation) could help us understand disk evolution and dispersal at different metallicities. Furthermore, our stellar spin evolution model includes several important effects that had previously been ignored (e.g., the stellar magnetic field strength and a realistic calculation of the disk lifetime). We encourage others to include our results as initial or input parameters in further spin evolution models that cover the stellar evolution toward and during the main sequence.