Optical properties of carbon grains: Influence on dynamical models of AGB stars

TL;DR

This study investigates how different laboratory-measured optical properties of amorphous carbon affect the structure, wind, and spectral features of dynamical models of dust shells around carbon-rich AGB stars.

Contribution

It provides a self-consistent modeling approach showing the impact of various amorphous carbon data sets on stellar wind properties and spectral energy distributions.

Findings

Mass loss is relatively unaffected by dust optical property variations.

Degree of condensation and outflow velocity are significantly influenced.

Spectral energy distributions vary widely with different dust data sets.

Abstract

For amorphous carbon several laboratory extinction data are available, which show quite a wide range of differences due to the structural complexity of this material. We have calculated self-consistent dynamic models of circumstellar dust-shells around carbon-rich asymptotic giant branch stars, based on a number of these data sets. The structure and the wind properties of the dynamical models are directly influenced by the different types of amorphous carbon. In our test models the mass loss is not severely dependent on the difference in the optical properties of the dust, but the influence on the degree of condensation and the final outflow velocity is considerable. Furthermore, the spectral energy distributions and colours resulting from the different data show a much wider spread than the variations within the models due to the variability of the star. Silicon carbide was also considered in the radiative transfer calculations to test its influence on the spectral energy distribution.