Dusty winds II. Observational Implications

TL;DR

This paper compares observational data of AGB stars with a radiatively driven dusty wind model, revealing the importance of dust drift and providing insights into dust properties and abundance in stellar outflows.

Contribution

It validates a steady-state wind model against observations, highlighting dust drift effects and consistent dust properties across different star types.

Findings

Model reproduces observed correlations among stellar wind properties.

Dust drift significantly influences wind structure.

Dust abundance in outflows is below the Galactic average.

Abstract

We compare observations of AGB stars and predictions of the Elitzur & Ivezic (2001) steady-state radiatively driven dusty wind model. The model results are described by a set of similarity functions of a single independent variable, and imply general scaling relations among the system parameters. We find that the model properly reproduces various correlations among the observed quantities and demonstrate that dust drift through the gas has a major impact on the structure of most winds. From data for nearby oxygen-rich and carbon-rich mass-losing stars we find that (1) the dispersion in grain properties within each group is rather small; (2) both the dust cross-section per gas particle and the dust-to-gas mass ratio are similar for the two samples even though the stellar atmospheres and grain properties are very different; (3) the dust abundance in both outflows is significantly below the Galactic average, indicating that most of the Galactic dust is not stardust - contrary to popular belief, but in support of Draine (2009). Our model results can be easily applied to recent massive data sets, such as the Spitzer SAGE survey of the Large Magellanic Cloud, and incorporated in galaxy evolution models.