3 research outputs found
Stellar evolution of massive stars with a radiative alpha-omega dynamo
Models of rotationally-driven dynamos in stellar radiative zones have
suggested that magnetohydrodynamic transport of angular momentum and chemical
composition can dominate over the otherwise purely hydrodynamic processes. A
proper consideration of the interaction between rotation and magnetic fields is
therefore essential. Previous studies have focused on a magnetic model where
the magnetic field strength is derived as a function of the stellar structure
and angular momentum distribution. We have adapted our one-dimensional stellar
rotation code, RoSE, to model the poloidal and toroidal magnetic field
strengths with a pair of time-dependent advection-diffusion equations coupled
to the equations for the evolution of the angular momentum distribution and
stellar structure. This produces a much more complete, though still reasonably
simple, model for the magnetic field evolution. Our model reproduces well
observed surface nitrogen enrichment of massive stars in the Large Magellanic
Cloud. In particular it reproduces a population of slowly-rotating
nitrogen-enriched stars that cannot be explained by rotational mixing alone
alongside the traditional rotationlly-enriched stars. The model further
predicts a strong mass-dependency for the dynamo-driven field. Above a
threshold mass, the strength of the magnetic dynamo decreases abruptly and so
we predict that more massive stars are much less likely to support a
dynamo-driven field than less massive stars.Comment: Accepted for publication in MNRAS. 15 pages, 13 figure