Ultraviolet and Infrared Observations of Stars with ``Quenched'' Chromospheres and the Nature of Mass Loss

Abstract

Previous observational evidence implies that the presence of Ca II emission, a chromospheric indicator, is correlated with the gas/dust ratio in the envelopes of red giant and supergiant stars. An attempt is made to determine whether this correlation can be generalized to all chromospheric activity indicators and the gas/dust ratio. New ultraviolet observations address the strength of UV emission features and the fraction of the total chromospheric flux emitted in various lines. Evidence is found that chromospheres are not completely quenched in the presence of dust, but that significant alteration of relative radiative loss patterns may occur. These observations are interpreted in terms of an instability that converts warm, chromospheric gas into near-surface dust grains and cool gas capable of supporting molecular masing. This supports the dust-driven mass loss scenario for red giant winds.