AAVSO: American Association of Variable Star Observers

What Kinds of Dust Exist in Circumstellar Shells of Miras?

Volume 25 number 2 (1997)

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Irene R. Little-Marenin
Stephen J. Little
CASA, CB 389

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.