Formation of dust grains in the winds of cool giants, PhD thesis 1992

TL;DR

This thesis develops a theoretical framework for dust formation in the winds of cool giant stars, demonstrating how radiation pressure on dust drives stellar winds and deriving related mass-loss formulas.

Contribution

It introduces an efficient moment method for dust growth modeling and applies it to self-consistently simulate dust-driven winds in AGB stars.

Findings

Radiation pressure on dust can drive stellar winds in cool giants.

A parameter study yields mass-loss formulas for AGB star winds.

The theory extends to heterogeneous grain condensation.

Abstract

Interstellar dust forms during stellar mass-loss events, occurring either during a star's giant phase or during supernova explosions. This PhD thesis provides an in-depth investigation into the theory of dust condensation and growth, specifically applied to the winds of cool giants such as Asymptotic Giant Branch (AGB) stars. The thesis begins with a theoretical description of the chemical reactions that initiate seed formation within a cooling flow. It then details an efficient mechanism - a moment method based on size-weighted moments of the grain size distribution - to compute dust evolution during growth. This theoretical framework is applied to dust-driven winds from carbon-rich AGB stars. By deriving wind equations and self-consistently incorporating dust formation, the research demonstrates that radiation pressure on dust forming in the expanding atmosphere can drive a stellar wind. Furthermore, a parameter study covering the giant region of the Hertzsprung-Russell (HR) diagram is used to derive mass-loss formulas for these winds. The final chapter expands the dust formation theory to investigate the condensation of heterogeneous grains.