The life cycles of Be viscous decretion discs: The case of ω CMa

Abstract

We analyzed V-band photometry of the Be star ω CMa, obtained during the last four decades, during which the star went through four complete cycles of disc formation and dissipation. The data were simulated by hydrodynamic models based on a time-dependent implementation of the viscous decretion disc (VDD) paradigm, in which a disc around a fast-spinning Be star is formed by material ejected by the star and driven to progressively larger orbits by means of viscous torques. Our simulations offer a good description of the photometric variability during phases of disc formation and dissipation, which suggests that the VDD model adequately describes the structural evolution of the disc. Furthermore, our analysis allowed us to determine the viscosity parameter α, as well as the net mass and angular momentum (AM) loss rates. We find that α is variable, ranging from 0.1 to 1.0, not only from cycle to cycle but also within a given cycle. Additionally, build-up phases usually have larger values of α than the dissipation phases. Furthermore, during dissipation the outward AM flux is not necessarily zero, meaning that ω CMa does not experience a true quiescence but, instead, switches between a high to a low AM loss rate during which the disc quickly assumes an overall lower density but never zero. We confront the average AM loss rate with predictions from stellar evolution models for fast-rotating stars, and find that our measurements are smaller by more than one order of magnitude.

arXiv comment16 pages, 16 figures

References in corpus (29)

• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• Accretion disc viscosity: how big is alpha?
• 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
• Kepler observations of variability in B-type stars
• A unifying explanation of complex frequency spectra of gamma Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves
• Viscous Transonic Decretion in Disks of Be Stars
• Dynamical Evolution of Viscous Disks around Be Stars. I: photometry
• Mass and angular momentum loss via decretion disks
• First direct detection of a Keplerian rotating disk around the Be star $\alpha$ Arae using the VLTI/AMBER instrument
• CHARA Array K'-band Measurements of the Angular Dimensions of Be Star Disks
• Populations of rotating stars II. Rapid rotators and their link to Be-type stars
• Non-LTE Monte Carlo Radiative Transfer: II. Non-Isothermal Solutions for Viscous Keplerian Disks
• Short-term variability and mass loss in Be stars I. BRITE satellite photometry of $\eta$ and $\mu$ Centauri
• The life cycles of Be viscous decretion discs: fundamental disc parameters of 54 SMC Be stars
• The life cycles of Be viscous decretion discs: time-dependent modelling of infrared continuum observations
• The first determination of the viscosity parameter in the circumstellar disk of a Be Star
• The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries
• Cyclic Variability of the Circumstellar Disc of the Be Star $\zeta$ Tau. II. Testing the 2D Global Disc Oscillation Model
• Revealing the structure of the outer disks of Be stars
• Be discs in binary systems I. Coplanar orbits
• Properties of the $\delta$ Scorpii Circumstellar Disk from Continuum Modeling
• Line-driven ablation of circumstellar disks: I. Optically thin decretion disks of classical Oe/Be stars
• Achernar: Rapid Polarization Variability as Evidence of Photospheric and Circumstellar Activity
• The pseudo-photosphere model for the continuum emission of gaseous discs
• Constraining the Physical Parameters of the Circumstellar Disk of chi Ophiuchi
• The Infrared Continuum Sizes of Be Star Disks
• Variable rotational line broadening in the Be star Achernar
• Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star $\beta$ CMi

Cited by in corpus (28)

• On the physical nature of accretion disc viscosity
• Prevalence of SED turndown among classical Be stars: Are all Be stars close binaries?
• gamma Cas stars: Normal Be stars with disks impacted by the wind of a helium-star companion?
• Growth and Dissipation of Be Star Discs in Misaligned Binary Systems
• The Be Star 66 Ophiuchi: 60 Years of Disk Evolution
• A Multi-observing-technique Study of the Dynamical Evolution of the Viscous Disk around the Be Star $\omega$ CMa
• 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)
• Short-term variability and mass loss in Be stars V. Space photometry and ground-based spectroscopy of $\gamma$ Cas
• Outbursts and stellar properties of the classical Be star HD 6226
• Formation and Destiny of White Dwarf and Be Star Binaries
• The Large Scale Behaviour in the Disk of $\delta$ Scorpii from 2000-2018
• Short-term variability and mass loss in Be stars VI. Frequency groups in $\gamma$ Cas detected by TESS
• Be star discs: powered by a non-zero central torque
• Superorbital periods of Be/X-ray binaries driven by stellar spin precession
• Modelling the observable behaviour of SXP 5.05
• Fast nodal precession of the disc around Pleione requires a broken disc
• Retrograde discs around one component of a binary are unstable to tilting
• A survey for variable young stars with small telescopes: VI -- Analysis of the outbursting Be stars NSW284, Gaia19eyy, and VES263
• V1294 Aql = HD 184279: A bad boy among Be stars or an important clue to the Be phenomenon?
• Long-term, orbital, and rapid variations of the Be star V923 Aql = HD 183656
• Strong Variability in AzV 493, an Extreme Oe-Type Star in the SMC
• Red Be stars in the Magellanic Clouds?
• Angular Momentum Loss Rates in Be Stars Determined by the Viscous Decretion Disc Model
• Study of a Sample of Faint Be Stars in the Exofield of CoRoT. Part III. Global Spectroscopic Characterization and Astrophysical Parameters of the Central Stars
• Irregular emission cycles in the Oe star HD 60848
• Hydrodynamical models of the $\beta$ Lyr A circumstellar disc
• Disc breaking through forced eccentricity growth