Computing the Polarimetric and Photometric Variability of Be Stars

Abstract

We investigate variations in the linear polarization as well as in the V -band and B -band color–magnitudes for classical Be star disks. We present two models: disks with enhanced disk density and disks that are tilted or warped from the stellar equatorial plane. In both cases, we predict variation in observable properties of the system as the disk rotates. We use a non-LTE radiative transfer code bedisk (Sigut & Jones) in combination with a Monte Carlo routine that includes multiple scattering (Halonen et al.) to model classical Be star systems. We find that a disk with an enhanced density region that is one order of magnitude denser than the disk’s base density shows as much as variability in the polarization while the polarization position angle varies by . The Δ V magnitude for the same system shows variations of up to mag while the Δ( B – V ) color varies by at most mag. We find that disks tilted from the equatorial plane at small angles of more strongly reflect the values of polarization and color–magnitudes reported in the literature than disks tilted at larger angles. For this model, the linear polarization varies by , the polarization position angle varies by , the Δ V magnitude varies up to 0.35 mag, and the Δ( B – V ) color varies by up to 0.1 mag. We find that the enhanced disk density models show ranges of polarization and color–magnitudes that are commensurate with what is reported in the literature for all sizes of the density-enhanced regions. From this, we cannot determine any preference for small or large density-enhanced regions.