Be discs in binary systems: II. Misaligned orbits

Abstract

We use a smoothed particle hydrodynamics (SPH) code to examine the effects of misaligned binary companions on Be star discs. We systematically vary the degree of misalignment between the disc and the binary orbit, as well as the disc viscosity and orbital period to study their effects on the density in the inner and outer parts of the disc. We find that varying the degree of misalignment, the viscosity, and the orbital period affects both the truncation radius and the density structure of the outer disc, while the inner disc remains mostly unaffected. We also investigate the tilting of the disc in the innermost part of the disc and find the tilt increases with radius until reaching a maximum around 5 stellar radii. The direction of the line of nodes, with respect to the equator of the central star, is found to be offset compared to the orbital line of nodes, and to vary periodically in time, with a period of half a orbital phase. We also compare the scale height of our discs with the analytical scale height of an isothermal disc, which increases with radius as $r^{1.5}$. We find that this formula reproduces the scale height well for both aligned and misaligned systems but underestimates the scale height in regions of the disc where density enhancements develop.

11 pages, 10 figures, to be published in MNRAS

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• Growth and Dissipation of Be Star Discs in Misaligned Binary Systems
• The Be Star 66 Ophiuchi: 60 Years of Disk Evolution
• Modelling decretion discs in Be/X-ray binaries
• To Be or not to Be: the role of rotation in modeling Galactic Be X-ray Binaries
• The frequency of Kozai-Lidov disc oscillation driven giant outbursts in Be/X-ray binaries
• The Role of Disk Tearing and Precession in the Observed Variability of Pleione
• Spiral Density Enhancements in Be Binary Systems
• The Large Scale Behaviour in the Disk of $\delta$ Scorpii from 2000-2018
• Visible and near-infrared spectro-interferometric analysis of the edge-on Be star $o$ Aquarii
• High-spatial-resolution simulations of Be star disks in binary systems: I. Structure and kinematics of coplanar disks
• Superorbital periods of Be/X-ray binaries driven by stellar spin precession
• Fast time optical variability in Be/X-ray binaries. Pulsation and rotation
• Fast nodal precession of the disc around Pleione requires a broken disc
• Long-term optical variability of high-mass X-ray binaries. III. Polarimetry