CP and related phenomena in the context of Stellar Evolution

TL;DR

This paper reviews magnetic and chemical phenomena in stars, focusing on fossil magnetic fields, their evolution, and the impact of macroscopic motions on surface abundances, supported by recent spectropolarimetric and asteroseismic findings.

Contribution

It synthesizes recent observational and theoretical advances on stellar magnetism, diffusion, and mixing processes, highlighting new evidence for fossil fields and their early origin.

Findings

Magnetic fields in Herbig Ae/Be stars are consistent with fossil field theory.

A lack of stars with magnetic fields below a few hundred gauss was confirmed.

Differences in interior abundance distributions can be tested via asteroseismology.

Abstract

We review the interaction in intermediate and high mass stars between their evolution and magnetic and chemical properties. We describe the theory of Ap-star `fossil' fields, before touching on the expected secular diffusive processes which give rise to evolution of the field. We then present recent results from a spectropolarimetric survey of Herbig Ae/Be stars, showing that magnetic fields of the kind seen on the main-sequence already exist during the pre-main sequence phase, in agreement with fossil field theory, and that the origin of the slow rotation of Ap/Bp stars also lies early in the pre-main sequence evolution; we also present results confirming a lack of stars with fields below a few hundred gauss. We then seek which macroscopic motions compete with atomic diffusion in determining the surface abundances of AmFm stars. While turbulent transport and mass loss, in competition with atomic diffusion, are both able to explain observed surface abundances, the interior abundance distribution is different enough to potentially lead to a test using asterosismology. Finally we review progress on the turbulence-driving and mixing processes in stellar radiative zones.