HR diagrams for dust driven winds around C-stars.

Radiation pressure on dust grains plays an important role in the mass loss mechanism of late type giants. We have constructed selfconsistent models of dust driven winds around carbon stars including a detailed treatment of dust formation covering a wide range of stellar parameters. In order to demonstrate the general dependence of the models on the stellar parameters, HR-diagrams are constructed with contour lines of constant mass loss rate. Important results are: (i) Dust driven winds are possible only in a certain region of the HRD. (ii) Dust driven winds are, in principle, capable of explaining many observed properties of AGB winds. (iii) The dust driven mass loss rate is a steep function of the stellar parameters and can be expected to increase strongly as the evolution of cool giants progresses.