Evolution of massive stars at very low metallicity including rotation and binary interactions

TL;DR

This paper reviews models of massive star evolution at very low metallicity, emphasizing the roles of rotation, magnetic fields, and binary interactions, and their implications for phenomena like gamma-ray bursts and chemical enrichment.

Contribution

It introduces new models that incorporate rotation, magnetic fields, and binarity, highlighting their impact on the evolution and end states of low-metallicity massive stars.

Findings

Rapid rotation leads to quasi-chemically homogeneous evolution.

Low metallicity stars lose little mass and angular momentum.

Binary interactions can significantly enhance rotational effects.

Abstract

We discuss recent models on the evolution of massive stars at very low metallicity including the effects of rotation, magnetic fields and binarity. Very metal poor stars lose very little mass and angular momentum during the main sequence evolution, and rotation plays a dominant role in their evolution. In rapidly rotating massive stars, the rotationally induced mixing time scale can be even shorter than the nuclear time scale throughout the main sequence. The consequent quasi-chemically homogeneous evolution greatly differs from the standard massive star evolution that leads to formation of red giants with strong chemical stratification. Interesting outcomes of such a new mode of evolution include the formation of rapidly rotating massive Wolf-Rayet stars that emit large amounts of ionizing photons, the formation of a long gamma-ray bursts and a hypernovae, and the production of large amounts of primary nitrogen. We show that binary interactions can further enhance the effects of rotation, as mass accretion in a close binary spins up the secondary.