Be discs in binary systems I. Coplanar orbits

Abstract

Be stars are surrounded by outflowing circumstellar matter structured in the form of decretion discs. They are often members of binary systems, where it is expected that the decretion disc interacts both radiatively and gravitationally with the companion. In this work we study how various orbital (period, mass ratio and eccentricity) and disc (viscosity) parameters affect the disc structure in coplanar systems. We simulate such binaries with the use of a smoothed particle hydrodynamics code. The main effects of the secondary on the disc are its truncation and the accumulation of material inwards of truncation. We find two cases with respect to the effects of eccentricity: (i) In circular or nearly circular prograde orbits, the disc maintains a rotating, constant in shape, configuration, which is locked to the orbital phase. The disc is smaller in size, more elongated and more massive for low viscosity parameter, small orbital separation and/or high mass ratio. (ii) Highly eccentric orbits are more complex, with the disc structure and total mass strongly dependent on the orbital phase and the distance to the secondary. We also study the effects of binarity in the disc continuum emission. Since the infrared and radio SED are sensitive to the disc size and density slope, the truncation and matter accumulation result in considerable modifications in the emergent spectrum. We conclude that binarity can serve as an explanation for the variability exhibited in observations of Be stars, and that our model can be used to detect invisible companions.

15 pages, 30 figures

References in corpus (24)

• Binary interaction dominates the evolution of massive stars
• Be/X-ray binaries
• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• A natural explanation for periodic X-ray outbursts in Be/X-ray binaries
• NLTE Monte Carlo Radiative Transfer: I. The Thermal Properties of Keplerian Disks around Classical Be Stars
• Viscous Effects on the Interaction between the Coplanar Decretion Disc and the Neutron Star in Be/X-Ray Binaries
• The Be/X-ray transient 4U 0115+63/V635 Cas I. A consistent model
• Accretion vs colliding wind models for the gamma-ray binary LS I +61 303: an assessment
• Viscous Transonic Decretion in Disks of Be Stars
• Dynamical Evolution of Viscous Disks around Be Stars. I: photometry
• Dynamical Tides in Rotating Binary Stars
• FUV Detection of the Suspected Subdwarf Companion to the Be Star 59 Cygni
• A Study of Pi Aquarii During a Quasi-normal Star Phase: Refined Fundamental Parameters and Evidence for Binarity
• The first determination of the viscosity parameter in the circumstellar disk of a Be Star
• Cyclic Variability of the Circumstellar Disc of the Be Star $\zeta$ Tau. II. Testing the 2D Global Disc Oscillation Model
• Modeling high-energy light curves of the PSR B1259-63/LS 2883 binary based on 3-D SPH simulations
• Properties of the $\delta$ Scorpii Circumstellar Disk from Continuum Modeling
• The pseudo-photosphere model for the continuum emission of gaseous discs
• Gamma-rays from cascades in close massive binaries containing energetic pulsars
• A Parameter Study of Classical Be Star Disk Models Constrained by Optical Interferometry
• Be discs in binary systems: II. Misaligned orbits
• The binary fraction and mass-ratio of Be and B stars: a comparative VLT/NACO study
• Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star $\beta$ CMi
• 2.5D global-disk oscillation models of the Be shell star ζ Tauri I. Spectroscopic and polarimetric analysis

Cited by in corpus (36)

• Be X-ray binaries in the SMC as indicators of mass transfer efficiency
• Investigating the lack of main-sequence companions to massive Be stars
• The life cycles of Be viscous decretion discs: time-dependent modelling of infrared continuum observations
• Photometric Variability of the Be Star Population
• Prevalence of SED turndown among classical Be stars: Are all Be stars close binaries?
• Revealing the structure of the outer disks of Be stars
• The Hot Companion and Circumbinary Disk of the Be Star HR 2142
• The life cycles of Be viscous decretion discs: The case of ω CMa
• Be discs in coplanar circular binaries: Phase-locked variations of emission lines
• A propelling neutron star in the enigmatic Be-star $\gamma$~Cassiopeia
• Be discs in binary systems: II. Misaligned orbits
• Growth and Dissipation of Be Star Discs in Misaligned Binary Systems
• The Be Star 66 Ophiuchi: 60 Years of Disk Evolution
• An investigation of the photometric variability of confirmed and candidate Galactic Be stars using ASAS-3 data
• Modelling decretion discs in Be/X-ray binaries
• Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $\nu$ Puppis (B7-8 IIIe)
• To Be or not to Be: the role of rotation in modeling Galactic Be X-ray Binaries
• Short-term variability and mass loss in Be stars V. Space photometry and ground-based spectroscopy of $\gamma$ Cas
• Formation and Destiny of White Dwarf and Be Star Binaries
• Spiral Density Enhancements in Be Binary Systems
• The Large Scale Behaviour in the Disk of $\delta$ Scorpii from 2000-2018
• Multi-wavelength observations of PSRJ 2032+4127 during the 2017 periastron passage
• A Spectroscopic Orbit for the late-type Be star $\beta$ CMi
• Visible and near-infrared spectro-interferometric analysis of the edge-on Be star $o$ Aquarii
• Superorbital modulation at GeV energies in the gamma-ray binary LS I +61 303
• High-spatial-resolution simulations of Be star disks in binary systems: I. Structure and kinematics of coplanar disks
• A new look into putative duplicity and pulsations of the Be star $\beta$ CMi
• Optical and near-infrared photometric monitoring of the transient X-ray binary A0538-66 with REM
• Modelling the periodical variations in multiband polarisation and photometry for discs of binary Be stars
• Fast time optical variability in Be/X-ray binaries. Pulsation and rotation
• Don't torque like that. Measuring compact object magnetic fields with analytic torque models
• Near-infrared Brightening around the Periastron Passages of the Gamma-ray Binary PSR B1259$-$63 /LS 2883
• Exploring membership and variability in NGC 7419: An open cluster rich in super giants and Be type stars
• Ultraviolet spectroscopy reveals a hot and luminous companion to the Be star+black hole candidate MWC 656
• Fluorescent Fe K line emission of gamma Cas stars II. Predictions for magnetic interactions and white-dwarf accretion scenarios
• Long-term optical variability of high-mass X-ray binaries. III. Polarimetry