Fast nodal precession of the disc around Pleione requires a broken disc

Abstract

Pleione is a Be star that is in a 218 day orbit with a low-mass binary companion. Recent numerical simulations have shown that a Be star disc can be subject to breaking when material is actively being fed into the inner parts of the disc. After breaking, the disc is composed of two rings: an inner ring that is anchored to the stellar equator and an outer ring that is free to nodally precess. A double ring disc may explain some of the observed variability in Pleione. We model the nodal precession of the outer disc ring that is driven by the companion on an observed timescale of $80.5\mathrm{yr}$. We find that the outer ring of a broken disc in a binary with an eccentricity of $e_{\mathrm{b}}=0.6$ can precess on the observed timescale and have an outer radius that is in rough agreement with the observed disc size. An unbroken disc model cannot fit both the observed precession rate and disc size. Suppression of Kozai-Lidov driven disc eccentricity is more likely for a high binary eccentricity if the disc extends to the tidal truncation radius.

Accepted for publication in MNRAS Letters

References in corpus (17)

• The Kozai-Lidov Mechanism in Hydrodynamical Disks
• Giant Outbursts in Be/X-ray Binaries
• Tidal Torques on Misaligned Disks in Binary Systems
• Tearing up a misaligned accretion disc with a binary companion
• Linear Analysis of the Evolution of Nearly Polar Low Mass Circumbinary Discs
• The Kozai-Lidov Mechanism in Hydrodynamical Disks. II. Effects of binary and disk parameters
• GW Ori: Interactions Between a Triple-star System and its Circumtriple Disk in Action
• Generalised warped disk equations
• On the Spin Period Distribution in Be/X-ray Binaries
• Polar planets around highly eccentric binaries are the most stable
• Misaligned accretion disc formation via Kozai-Lidov oscillations
• Be discs in binary systems: II. Misaligned orbits
• Growth and Dissipation of Be Star Discs in Misaligned Binary Systems
• Modelling decretion discs in Be/X-ray binaries
• Circumbinary disk evolution in the presence of an outer companion star
• The Role of Disk Tearing and Precession in the Observed Variability of Pleione
• Eccentric neutron star disk driven type II outburst pairs in Be/X-ray binaries

Cited by in corpus (1)

• Superorbital periods of Be/X-ray binaries driven by stellar spin precession