Line-driven ablation of circumstellar disks: I. Optically thin decretion disks of classical Oe/Be stars

Abstract

The extreme luminosities of hot, massive stars drive strong stellar winds through UV line-scattering. For OB stars with an orbiting circumstellar disk, we explore the effect of such line-scattering in ablating disk material, initially focusing on the marginally optically thin decretion disks of classical Oe and Be stars. For this we apply a multi-dimensional radiation-hydrodynamics code, assuming optically thin ray tracing for the stellar continuum and a multi-ray Sobolev treatment of the line transfer. This accounts for desaturation of line-absorption by Keplerian shear in the disk, and associated driving by non-radial photons. Results show dense, intermediate-speed surface ablation, consistent with the strong, blue-shifted absorption seen in UV wind lines of Be shell stars. The asymptotic ablation rate is typically an order-unity factor times the stellar wind mass loss rate, leading to disk destruction times of order months to years for Be disks, consistent with observations. The much stronger radiative forces of O stars reduce this time to order days, making sustaining a disk difficult, and so providing a natural explanation for the rarity of Galactic Oe stars. Additionally, the weakened line-driving at lower metallicity implies both a reduction in the winds that help spin-down stars from near-critical rotation, and in the ablation of decretion disks, thus providing a natural explanation for the higher fraction of Classical Be stars, and the presence of Oe stars, in the Magellanic Clouds. We conclude with a discussion of future extensions to study line-driven ablation of denser, optically thick, accretion disks around pre-main-sequence massive stars.

arXiv comment14 pages, 20 figures

References in corpus (25)

• Mass-loss predictions for O and B stars as a function of metallicity
• A new calibration of stellar parameters of Galactic O stars
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• Mass loss from hot massive stars
• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• Gravity darkening in rotating stars
• A CHARA Array Survey of Circumstellar Disks around Nearby Be-type Stars
• The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds
• Effects of metallicity, star-formation conditions, and evolution in B and Be stars. II: Small Magellanic Cloud, field of NGC 330
• Populations of rotating stars. - I. Models from 1.7 to 15 Msun at Z = 0.014, 0.006, and 0.002 with Ω/Ωcrit between 0 and 1
• Mass and angular momentum loss via decretion disks
• The interaction of a giant planet with a disc with MHD turbulence I: The initial turbulent disc models
• Effects of metallicity, star formation conditions and evolution in B and Be stars. I: Large Magellanic Cloud, field of NGC 2004
• The first determination of the viscosity parameter in the circumstellar disk of a Be Star
• Line-driven disk wind models with an improved line force
• Cyclic Variability of the Circumstellar Disc of the Be Star $\zeta$ Tau. II. Testing the 2D Global Disc Oscillation Model
• First spectro-interferometric survey of Be stars I. Observations and constraints on the disks geometry and kinematics
• On the class of Oe stars
• On the presence and absence of disks around O-type stars
• The Infrared Continuum Sizes of Be Star Disks
• Dynamics of Line-Driven Winds from Disks in Cataclysmic Variables. I. Solution Topology and Wind Geometry
• Classical Oe Stars in the Field of the Small Magellanic Cloud
• The changing UV and X-ray properties of the Of?p star CPD -28 2561
• Line Forces in Keplerian Circumstellar Disks and Precession of Nearly Circular Orbits

Cited by in corpus (36)

• First hydrodynamics simulations of radiation forces and photoionization feedback in massive star formation
• Forming spectroscopic massive proto-binaries by disk fragmentation
• The life cycles of Be viscous decretion discs: fundamental disc parameters of 54 SMC Be stars
• Photometric Variability of the Be Star Population
• Chasing discs around O-type (proto)stars - ALMA evidence for an SiO disc and disc wind from G17.64+0.16
• Jets and outflows of massive protostars - From cloud collapse to jet launching and cloud dispersal
• The life cycles of Be viscous decretion discs: The case of ω CMa
• Short-term variability and mass loss in Be stars III. BRITE and SMEI satellite photometry of 28 Cygni
• Outbursts and Disk Variability in Be Stars
• Be discs in binary systems: II. Misaligned orbits
• Dynamically inflated wind models of classical Wolf-Rayet stars
• Radiation-Hydrodynamics with MPI-AMRVAC: Flux-Limited Diffusion
• Disruption of circumstellar discs by large-scale stellar magnetic fields
• A Multi-observing-technique Study of the Dynamical Evolution of the Viscous Disk around the Be Star $\omega$ CMa
• An Updated Formalism For Line-Driven Radiative Acceleration and Implications for Stellar Mass Loss
• Intriguing X-ray and optical variations of the gamma Cas analog HD45314
• 3D radiative transfer: Continuum and line scattering in non-spherical winds from OB stars
• Line-driven ablation of circumstellar discs: III. Accounting for and analyzing the effects of continuum optical depth
• The X-ray emission of gamma Cassiopeiae during the 2020-2021 disc eruption
• Two-dimensional modeling of density and thermal structure of dense circumstellar outflowing disks
• Line-driven ablation of circumstellar discs: IV. The role of disc ablation in massive star formation and its contribution to the stellar upper mass limit
• Method and new tabulations for flux-weighted line-opacity and radiation line-force in supersonic media
• 3D MHD simulations and synthetic radio emission from an oblique rotating magnetic massive star
• X-ray response to disk evolution in two gamma-Cas stars
• High-spatial-resolution simulations of Be star disks in binary systems: I. Structure and kinematics of coplanar disks
• Simulations of the line-driven instability in magnetic hot star winds
• Co-existence and switching between fast and $\Omega$-slow wind solutions in rapidly rotating massive stars
• $\Omega$-Slow Solutions and Be Star Disks
• HST/COS Spectra of the Wind Lines of VFTS 102 and 285
• Classical Be stars
• An extensive spectroscopic time series of three Wolf-Rayet stars -- II. A search for wind asymmetries in the dust-forming WC7 binary WR137
• Angular Momentum Loss Rates in Be Stars Determined by the Viscous Decretion Disc Model
• Study of the transient nature of classical Be stars using multi-epoch optical spectroscopy
• Irregular emission cycles in the Oe star HD 60848
• Spectroscopic Line Modeling of the Fastest Rotating O-type Stars
• Revisiting Viscous Transonic Decretion Disks of Be Stars