Non-equilibrium chemistry and dust formation in AGB stars as probed by SiO line emission

2007/05/18 by F. L. Schoeier, Schoeier, F. L., H. Olofsson +9
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #FOS: Physical sciences #Stellar, planetary, and galactic studies

paper · pdf · doi:10.48550/arxiv.0705.2651

openalex publication_date 2007/05/18 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28

Abstract

We have performed high spatial resolution observations of SiO line emission for a sample of 11 AGB stars using the ATCA, VLA and SMA interferometers. Detailed radiative transfer modelling suggests that there are steep chemical gradients of SiO in their circumstellar envelopes. The emerging picture is one where the radial SiO abundance distribution starts at an initial high abundance, in the case of M-stars consistent with LTE chemistry, that drastically decreases at a radius of ~1E15 cm. This is consistent with a scenario where SiO freezes out onto dust grains. The region of the wind with low abundance is much more extended, typically ~1E16 cm, and limited by photodissociation. The surpisingly high SiO abundances found in carbon stars requires non-equilibrium chemical processes.

Related

• The transition from carbon dust to silicates production in low-metallicity AGB and SAGB stars
• The physics and chemistry of circumstellar envelopes of S-stars on the AGB
• Molecular dust precursors in envelopes of oxygen-rich AGB stars and red\n supergiants
• Starlight and Sandstorms: Mass Loss Mechanisms on the AGB
• The mass-loss rates and molecular abundances of S-type AGB stars