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INFRARED EMISSION AND DYNAMICS OF OUTFLOWS IN LATE-TYPE STARS

The dynamical structure and infrared emission of winds around late-type stars are studied in a self-consistent model that couples the equations of motion and radiative transfer. Both the dynamics and IR spectrum of the solution are fully characterized by the flux averaged optical depth. Five types of dust grains are considered: astronomical silicate, SiC, crystalline olivine, graphite and amorphous carbon as well as mixtures. Analysis of infrared signatures provides constraints on the grain chemical composition and indications for the simultaneous existence of silicate and carbon grains. The region of parameter space where radiation pressure can support a given mass-loss rate is identified and a new method to derive mass loss rates from IR data is presented. IRAS LRS classes are associated with optical depth for various grain materials and the regions of color-color diagrams expected to be populated by late-type stars are identified. We show that cirrus emission can severely affect point source measurements to the extent that their listed IRAS long wavelength fluxes are unreliable. After accounting for cirrus contamination, essentially all IRAS point sources located in the relevant regions of the color-color diagrams can be explained as late-type stars.