Influence of the Metal Abundances on the Dust-driven Winds of LPVs

Ch. Helling, T.U. Arndt and E. Sedlmayr

Astronomische Gesellschaft Abstract Series, Vol. 17., (2000)

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Abstract:

Dust formation is a widespread phenomenon and has been theoretically studied in the frame work of circumstellar envelopes (CSE) of late type stars with solar metallicity. Dust acts as an important dynamic component in such luminous objects due to its large absorption coefficient (at least 100*kappagas). The dust formation itself depends sensitively on the chemical composition of the gas as well as the thermodynamic conditions in the CSE.

This presentation concerns time-dependent models of dust forming long-periodic variables (LPVs, see Fleischer et al.) which exhibit a non-solar metallicity designed to resemble that of the Large Magellanic Cloud (LMC). The elemental abundances affect the composition of the molecular gas and thereby the dust formation via the amount of condensible material but also on the temperature and density structure of the CSE via radiative transfer effects. Models of different metallicities (solar and LMC), where the gas opacity has been approximated by its Planck mean, are examined with regard to the changes in the efficiency of the mass loss of dust-driven winds.

Keywords:

Hydrodynamics -- Stars: circumstellar matter -- Stars: carbon -- Stars: mass--loss -- Stars: AGB -- Stars: winds, outflows