Dust formation in winds of long-period variables
III. Dynamical models and confirmation of a dust-induced kappa-mechanism

S. Höfner, M.U. Feuchtinger and E.A. Dorfi

We present self-consistent dynamical models for purely dust driven winds of C-rich AGB stars which are based on the coupled system of radiation hydrodynamics and time-dependent dust formation and growth. Investigating the dependence of the solution on the relative abundance of carbon to oxygen (i.e. the amount of condensable material) for several sets of stellar parameters we obtain stationary dust driven winds as well as solutions with periodic dust formation and creation of shock waves without applying a variable inner boundary to simulate a pulsation of the underlying star. Model series with certain stellar parameters show a transition from stationary winds to time-dependent solutions with discrete dust layers and shock waves as the carbon/oxygen abundance ratio exceeds a critical value. Summarizing the results, our calculations demonstrate that the limit case of stationary dust driven winds can be reproduced using the full, time-dependent code and furthermore provide an independent confirmation of the dust-induced kappa-mechanism proposed by Fleischer et al. (1994).

A&A 279, 815