Two-dimensional modeling of density and thermal structure of dense circumstellar outflowing disks

Abstract

Context. Evolution of massive stars is affected by a significant loss of mass either via (nearly) spherically symmetric stellar winds or by aspherical mass-loss mechanisms, namely the outflowing equatorial disks. However, the scenario that leads to the formation of a disk or rings of gas and dust around massive stars is still under debate. Aims. We study the hydrodynamic and thermal structure of optically thick, dense parts of outflowing circumstellar disks that may be formed around various types of critically rotating massive stars, for example, Be stars, B[e] supergiant (sgB[e]) stars or Pop III stars. Methods. We specify the optical depth of the disk along the line-of-sight from stellar poles. Within the optically thick dense region we calculate the vertical disk thermal structure using the diffusion approximation while for the optically thin outer layers we assume a local thermodynamic equilibrium with the impinging stellar irradiation. We use two of our own types of hydrodynamic codes: two-dimensional operator-split numerical code and unsplit code based on the Roe's method. Results. Our models show the geometric distribution and contribution of viscous heating that begins to dominate in the central part of the disk. In the models of dense viscous disks the viscosity increases the central temperature up to several tens of thousands of Kelvins. The high mass-loss rates and high viscosity lead to instabilities with significant waves or bumps in density and temperature in the very inner disk region. Conclusions. The two-dimensional radial-vertical models of dense outflowing disks including the full Navier-Stokes viscosity terms show very high temperatures that are however limited to only the central disk cores inside the optically thick area, while near the edge of the optically thick region the temperature may be low enough for the existence of neutral hydrogen.

24 pages, 21 figures

References in corpus (13)

• Athena: A New Code for Astrophysical MHD
• The Thermal Structure of the Circumstellar Disk Surrounding the Classical Be Star gamma Cassiopeia
• Non-LTE Monte Carlo Radiative Transfer: II. Non-Isothermal Solutions for Viscous Keplerian Disks
• Dust-driven viscous ring-instability in protoplanetary disks
• Revealing the structure of the outer disks of Be stars
• Line-driven ablation of circumstellar disks: I. Optically thin decretion disks of classical Oe/Be stars
• Computing Limb Darkening Coefficients from Stellar Atmosphere Models
• Neutral material around the B[e] supergiant star LHA 115-S 65: An outflowing disk or a detached Keplerian rotating disk?
• Be Star Disk Models in Consistent Vertical Hydrostatic Equilibrium
• Molecular emission from GG Car's circumbinary disk
• Time-dependent modeling of extended thin decretion disks of critically rotating stars
• Magnetorotational instability in decretion disks of critically rotating stars and the outer structure of Be and Be/X-ray disks
• On the hydrogen neutral outflowing disks of B[e] supergiants

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