Multiple Molecular Winds in Evolved Stars I. A Survey of CO(2-1) and CO(3-2) Emission from 45 Nearby AGB Stars

This paper describes observations of a new phenomenon in evolved mass-losing AGB stars: the presence of two winds with different expansion velocities. CO(2-1) and CO(3-2) line emission was observed for 45 AGB stars at high velocity resolution and double winds found in 20% of the sample. Highly asymmetric lines were found in six other stars. The data tentatively suggest that double winds occur when the star undergoes a change (pulsational mode, chemical composition) and that the very narrow components represent the onset of a new phase of mass loss.