Gas and Dust Mass Loss of O-rich AGB-stars

Kapitel i bok, 2008

We present results from systematic surveys and subsequent modelling of circumstellar CO and SiO radio line emission of oxygen-rich semiregular and irregular variables of types SRa, SRb, and Lb, respectively. Results from high spatial resolution observations of a subsample of these objects with a more complex velocity structure in their CO profiles are presented and show clear evidence for deviations from the simple picture of spherically symmetric mass loss. The observations can be interpreted in terms of disks and/or axially symmetric outflows. Moreover, some insights into the thermal emission from dust particles formed around these late type variables are presented. An identification of metal oxides and amorphous silicates in low and intermediate mass loss rate objects has been possible.