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What Kinds of Dust Exist in Circumstellar Shells of Miras?

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Irene R. Littled-Marenin

Whitin Observatory

Wellesley College

Wellesley, MA 02181

Stephen J. Little

CASA, CB 389

University of Colorado

Boulder, CO 80309

Presented at the AAVSO Session on Mira Stars (part of the 85th Annual Meeting), November 1, 1996

Abstract

Mira variables lose mass which slowly expands into a circumstellar shell surrounding the star. Dust forms in the shell by condensation as the shell cools. The presence of dust in detected by infrared (IR) observations that record the general infrared emission from the cooler dust, as well as by IR spectral scans that detect emission features from the dust. These scans have revealed that the composition of dust in both oxygen- and carbon-rich stars is produced by a larger variety of dust grains than had been anticipated, and that the dust shows variation in phase with the visual light curve.