Dust formation in winds of long-period variables

V. The influence of micro-physical dust properties in carbon stars

¹ Department of Astronomy & Space Physics, Uppsala University, PO Box 515, 751 20 Uppsala, Sweden e-mail: hoefner@astro.uu.se
² Astronomical Obs., NBIfAFG, Copenhagen University, Juliane Maries Vej 30, 2100 Copenhagen, Denmark e-mail: anja@astro.ku.dk
³ Rüti, Switzerland e-mail: rita@gautschy.ch

Corresponding author: A. C. Andersen, anja@astro.ku.dk

Received: 21 October 2002
Accepted: 7 January 2003

Abstract

We present self-consistent dynamical models for dust-driven winds of carbon-rich AGB stars. The models are based on the coupled system of frequency-dependent radiation hydrodynamics and time-dependent dust formation. We investigate in detail how the wind properties of the models are influenced by the micro-physical properties of the dust grains that are required by the description of grain formation. The choice of dust parameters is significant for the derived outflow velocities, the degrees of condensation and the resulting mass-loss rates of the models. In the transition region between models with and without mass-loss the choice of micro-physical parameters turns out to be very significant for whether a particular set of stellar parameters will give rise to a dust-driven mass-loss or not. We also calculate near-infrared colors to test how the dust parameters influence the observable properties of the models, however, at this point we do not attempt to fit particular stars.