On the Intrinsic Continuum Linear Polarization of Classical Be Stars: The Effects of Metallicity and One-Armed Density Perturbations

TL;DR

This paper explores how metallicity and one-armed density perturbations influence the linear polarization signatures of classical Be stars, revealing potential diagnostic tools for stellar disk properties and dynamics.

Contribution

It introduces the effects of metallicity and non-axisymmetric density oscillations on polarization, providing new insights into Be star disk characteristics.

Findings

Metallicity affects disk temperature but not the Balmer jump frequency.

Non-axisymmetric density perturbations cause observable polarization variations.

Polarimetric signatures can indicate the presence of disk oscillations.

Abstract

We report on the effects of two disk properties on the continuum linear polarization signature of classical Be stars. First, we investigate the effect of including metallicity in computing the thermal structure of the circumstellar gas on the resulting polarimetric Balmer jump. The Balmer jump is a distinguishing feature of the polarization signature in these objects and, as such, can be used as a tool for differentiating classical Be stars from similar H alpha-emitters identified through conventional photometric techniques. We find that although low-metallicity environments will have hotter disk temperatures on average, the temperature change alone cannot account for the discrepancy in the frequency of Balmer jumps between low-metallicity and solar-metallicity stellar populations. Second, we investigate the effect of including a global one-armed oscillation in the gas density distribution of the modeled disk. We find that a non-axisymmetric perturbation pattern yields discernible variations in the predicted polarization level. If these density oscillations are present in the inner region of classical Be star disks, the polarimetric variations should produce a periodic signature which can help characterize the dynamical nature of the gas near the star.