Mid-Infrared Observations of Mass-Losing Red Giants
Within the past 3 years, mid-ir imagers have become available at 10-meter class telescopes. As a result, it is now possible to spatially resolve many sources which previously appeared to be point-like, and here we report mid-infrared observations at Keck of two stars, L2 Pup and OH 231.8+4.2. For L2 Pup, one of the nearest mass-losing red giants, we find that the wind may be driven by the stellar pulsations, with radiation pressure on dust being relatively unimportant. The stellar pulsations that drive the wind may be nonradial. For OH 231.8+4.2, we find both an extended bipolar flow and an unresolved central source. We suggest that the unresolved central source can be explained by an opaque, flared disk with an outer radius of 5 × 1015 cm and an outer temperature of ~130 K. One possible model to account for this flaring is that the material in the disk is orbiting the central star and not simply undergoing a radial expansion
KeywordsCentral Star Circumstellar Envelope Asymptotic Giant Branch Star Bipolar Outflow Stellar Pulsation
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