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| Paper: |
Starlight and Sandstorms: Mass Loss Mechanisms on the AGB |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
193 |
| Authors: |
Höfner, S. |
| Abstract: |
There are strong observational indications that the dense slow winds
of cool luminous AGB stars are driven by radiative pressure on dust
grains which form in the extended atmospheres resulting from
pulsation-induced shocks. For carbon stars, detailed models of
outflows driven by amorphous carbon grains show good agreement with
observations. Some still existing discrepancies may be due to a
simplified treatment of cooling in shocks, drift of the grains
relative to the gas, or effects of giant convection cells or
dust-induced pattern formation. For stars with C/O < 1, recent
models indicate that absorption by silicate dust is probably
insufficient to drive their winds. A possible alternative is
scattering by Fe-free silicate grains with radii of a few tenths of
a micron. In this scenario one should expect less circumstellar
reddening for M- and S-type AGB stars than for C-stars with
comparable stellar parameters and mass loss rates. |
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