The transport of angular momentum for massive stars I. Formation of slowly rotating WNE stars

TL;DR

This paper models the formation of slowly rotating WNE stars by incorporating internal gravity waves and magnetic instabilities, successfully explaining their slow rotation through enhanced angular momentum transfer mechanisms.

Contribution

It introduces improved prescriptions for internal gravity waves and magnetic Tayler instability into stellar evolution models, demonstrating their effectiveness in producing slowly rotating WNE stars.

Findings

Models reproduce slow rotation of WNE stars

Enhanced angular momentum transfer mechanisms are effective

Supports the existence of predicted stellar populations

Abstract

The evolutionary scenario of early-type nitrogen-sequence Wolf-Rayet (WNE) stars predicts a slowly rotating subclass that typically forms after the red supergiant (RSG) phase. Their slow rotation rates are attributed to stellar winds that remove angular momentum transferred outward during core contraction. We incorporate improved prescriptions for internal gravity waves and the magnetic Tayler instability into single massive star evolution models. Our simulations successfully produce slowly rotating WNE stars and determine optimal parameters for both mechanisms ($A \ge 10$ for internal gravity waves (IGWs), $\alpha = 0.01$ for revised Tayler instability (TSF)). The results demonstrate that the efficiency of angular momentum transfer in massive stars is significantly enhanced compared to low-mass stars, both processes can self-consistently explain the slow rotation of WNE stars, confirming their efficiency in angular momentum redistribution and providing crucial theoretical support for the existence of this predicted stellar population.