On the Intrinsic Continuum Linear Polarization of Classical Be Stars during Disk Growth and Dissipation

TL;DR

This paper models the intrinsic linear polarization of classical Be stars during disk formation and dissipation, demonstrating how polarimetric data can reveal disk evolution and mass-loss mechanisms.

Contribution

It introduces a Monte Carlo radiative transfer approach with self-consistent thermal structure calculations to analyze polarization spectra during disk changes.

Findings

Polarization features originate from different disk regions.

Self-consistent thermal modeling affects wavelength-dependent polarization.

Polarimetric observations can trace disk evolution and inform mass-loss mechanisms.

Abstract

We investigate the intrinsic continuum linear polarization from axisymmetric density distributions of gas surrounding classical Be stars during the formation and dissipation of their circumstellar disks. We implement a Monte Carlo calculation of the Stokes parameters with the use of the non-LTE radiative transfer code of Sigut & Jones (2007) to reproduce the continuous polarimetric spectra of classical Be stars. The scattering of light in the nonspherical circumstellar envelopes of classical Be stars produces a distinct polarization signature that can be used to study the physical nature of the scattering environment. In this paper, we highlight the utility of polarimetric measurements as important diagnostics in the modeling of these systems. We illustrate the effects of using self-consistent calculation of the thermal structure of the circumstellar gas on the characteristic wavelength-dependence of the polarization spectrum. In showing that the principal features of the polarization spectrum originate from different parts of the disk, we emphasize the capability of polarimetric observations to trace the evolution of the disk on critical scales. We produce models that approximate the disk formation and dissipation periods and illustrate how the polarimetric properties of these systems can have a pivotal role in determining the mechanism for mass decretion from the central star.