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

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.

Accepted to ApJS on July 22, 2013

References in corpus (5)

• The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds
• The Thermal Structure of the Circumstellar Disk Surrounding the Classical Be Star gamma Cassiopeia
• Be phenomenon in open clusters: Results from a survey of emission-line stars in young open clusters
• On the Intrinsic Continuum Linear Polarization of Classical Be Stars during Disk Growth and Dissipation
• The Role of Evolutionary Age and Metallicity in the Formation of Classical Be Circumstellar Disks II. Assessing the Evolutionary Nature of Candidate Disk Systems

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• Modelling the periodical variations in multiband polarisation and photometry for discs of binary Be stars
• Computing the Photometric and Polarimetric Variability of Be Stars
• Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars
• Long-term optical variability of high-mass X-ray binaries. III. Polarimetry