Polarization from the Structured Envelopes of Cool Evolved Stars

TL;DR

This paper explores how structured envelopes around cool evolved stars can produce measurable polarization signals through electron scattering, influenced by envelope shape and illumination anisotropy.

Contribution

It introduces preliminary models of polarization from cool star envelopes considering non-spherical shapes and brightness variations, highlighting potential for higher polarization from dust and molecular scattering.

Findings

Polarizations are typically very small, around hundredths of a percent.

Non-spherical envelopes and anisotropic illumination can generate net polarization.

Dust and molecular scattering may lead to higher polarization levels.

Abstract

We present preliminary calculations of electron scattering polarizations from models of structured cool star envelopes. We note that net polarizations from unresolved sources can result from non-spherical scattering envelopes and/or anisotropic illumination from a photosphere that has brightness variations. The resultant polarizations are quite small (hundreths of a percent); however, Rayleigh scattering from molecular opacity and/or dust scattering from the more extended envelope under similar considerations may produce higher polarizations.