Magnetic Fields around (post-)AGB stars and (Pre-)Planetary Nebulae

TL;DR

This paper reviews observational evidence for strong magnetic fields in evolved stars and discusses how future polarization observations could clarify their role in shaping stellar outflows and mass-loss during late stellar evolution.

Contribution

It highlights the potential of upcoming polarization observations to map magnetic fields from AGB stars to planetary nebulae, emphasizing their possible influence on stellar outflows.

Findings

Magnetic fields are prevalent in (post-)AGB star envelopes.

Magnetic field structures are maintained over large distances from the star.

Magnetic fields may influence stellar outflow shaping and mass-loss.

Abstract

Observational evidence for strong magnetic fields throughout the envelopes of evolved stars is increasing. Many of the instruments coming on line in the near-future will be able to make further contributions to this field. Specifically, maser polarization observations and dust/line polarization in the sub-mm regime has the potential to finally provide a definite picture of the magnetic field strength and configuration from the Asymptotic Giant Branch (AGB) all the way to the Planetary Nebula phase. While current observations are limited in sample size, strong magnetic fields appear ubiquitous at all stages of (post-)AGB evolution. Recent observations also strongly support a field structure that is maintained from close to the star to several thousands of AU distance. While its origin is still unclear, the magnetic field is thus a strong candidate for shaping the stellar outflows on the path to the planetary nebula phase and might even play a role in determining the stellar mass-loss.