Global Disk Oscillations in Binary Be Stars

TL;DR

This study investigates how binary interactions influence global disk oscillations in Be stars, revealing that disk size and binary parameters affect the oscillation periods and confinement, with implications for observed V/R variations.

Contribution

The paper introduces a 3D model of disk oscillations in binary Be stars, highlighting the effects of binary parameters on mode confinement and oscillation periods, which was not previously detailed.

Findings

Oscillations are well confined in disks larger than a few tens of stellar radii.

Oscillation period is largely independent of binary parameters in large disks.

In smaller disks, the period increases with orbital separation and decreases with binary mass ratio.

Abstract

We study the effects of the tidal interaction with the companion, via orbital separation and binary mass ratio, on the global one-armed oscillation modes in disks around binary Be stars. Our model takes into account the three-dimensional effect that contributes to the mode confinement, which was recently found by Ogilvie(2008). We find that the one-armed oscillations are well confined in systems with disks larger than a few tens of stellar radii. In such systems, the oscillation period depends little on the binary parameters. On the other hand, in systems with smaller disks, where the mode confinement is incomplete, the oscillation period increases with increasing orbital separation and/or decreasing binary mass ratio. The eigenmode is insensitive to the spectral type of the central star. Our results suggest that the dependence of V/R oscillation period on the orbital separation and binary mass ratio should be observed only in short period binary systems, and that, for systems with a similar orbital period, those with higher mass ratios will show shorter V/R variations.