Three-component modeling of C-rich AGB star winds I. Method and first results

Abstract

Radiative acceleration of newly-formed dust grains and transfer of momentum from the dust to the gas plays an important role for driving winds of AGB stars. Therefore a detailed description of the interaction of gas and dust is a prerequisite for realistic models of such winds. In this paper we present the method and first results of a three-component time-dependent model of dust-driven AGB star winds. With the model we plan to study the role and effects of the gas-dust interaction on the mass loss and wind formation. The wind model includes separate conservation laws for each of the three components of gas, dust and the radiation field and is developed from an existing model which assumes position coupling between the gas and the dust. As a new feature we introduce a separate equation of motion for the dust component in order to fully separate the dust phase from the gas phase. The transfer of mass, energy and momentum between the phases is treated by interaction terms. We also carry out a detailed study of the physical form and influence of the momentum transfer term (the drag force) and three approximations to it. In the present study we are interested mainly in the effect of the new treatment of the dust velocity on dust-induced instabilities in the wind. As we want to study the consequences of the additional freedom of the dust velocity on the model we calculate winds both with and without the separate dust equation of motion. The wind models are calculated for several sets of stellar parameters. We find that there is a higher threshold in the carbon/oxygen abundance ratio at which winds form in the new model. The winds of the new models, which include drift, differ from the previously stationary winds, and the winds with the lowest mass loss rates no longer form.

15 pages, 5 figures, accepted by A&A

References in corpus (2)

• Origin of quasi-periodic shells in dust forming AGB winds
• On the Formation of Multiple-Shells Around Asymptotic Giant Branch Stars

Cited by in corpus (16)

• An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars
• On the reliability of mass-loss-rate estimates for AGB stars
• A Spitzer mid-infrared spectral survey of mass-losing carbon stars in the Large Magellanic Cloud
• Infrared Photometry and Evolution of Mass-Losing AGB Stars I. Carbon Stars Revisited
• The Formation and Evolution of Wind-Capture Disks In Binary Systems
• Infrared Photometry and Evolution of Mass-Losing AGB Stars. II. Luminosity and Colors of MS and S Stars
• Radiation pressure and pulsation effects on the Roche lobe
• Three-component modeling of C-rich AGB star winds. II. The effects of drift in long-period variables
• Three-component modeling of C-rich AGB star winds III. Micro-physics of drift-dependent dust formation
• Three-component modeling of C-rich AGB star winds IV. Revised interpretation with improved numerical descriptions
• Three-component modelling of C-rich AGB star winds V. Effects of frequency-dependent radiative transfer including drift
• Oblique Alfvén waves in a stellar wind environment with dust particles charged by inelastic collisions and by photoionization
• Group velocity of obliquely propagating Alfvén waves in a magnetized dusty plasma
• Three-component modelling of O-rich AGB star winds I. Effects of drift using forsterite
• Formation of chondrules in radiative shock waves I. First results, spherical dust particles, stationary shocks
• Dynamic atmosphere and wind models of C-type asymptotic giant branch stars. Influences of dust optical data on mass loss and observables