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| Paper: |
Extended Atmospheres of AGB Stars: Modeling and Measurement |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
83 |
| Authors: |
Ireland, M. J. |
| Abstract: |
Encoded in the time- and wavelength-dependent properties of pulsating
AGB stars are the underlying fundamental parameters of mass,
composition and evolutionary state. However, the standard technique of
placing stars on an HR diagram, even with the aid of pulsation periods,
cannot be done easily for extended AGB stars because of the
difficulty of defining a radius or temperature. The atmospheres of Mira
variables are so extended that the optical depth unity radius can vary
by a factor of ∼3 over the energetically important region of the
spectrum. Many important constituents in the radiative transfer are
far from local thermodynamic equilibrium, and for the coolest stars,
the process of dust formation and destruction requires a
time-dependent model of grain growth. I will describe the challenges
and some of the solutions to modeling these atmospheres, and will
describe the utility of different kinds of observations in helping
understand both fundamental parameters and chaotic processes in
complex AGB atmospheres. |
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