Dynamic model atmospheres of AGB stars
II. Synthetic near infrared spectra of carbon stars

R. Loidl, S. Höfner, U.G. Jørgensen, B. Aringer

We have calculated synthetic opacity sampling spectra for carbon-rich Asymptotic Giant Branch (AGB) stars based on dynamic model atmospheres presented in the first paper of this series. We discuss how different model parameters influence the resulting synthetic spectra and how the spectra vary with phase. The molecules included are: CO, CH, CN, C2, HCN, C2H2, and C3. We show in which atmospheric layers the different molecules form, in an attempt to understand the qualitatively different variations with pulsation phase exhibited by various spectral features. Almost all features are blends of transitions from more than one molecule, and we therefore identify the most important transitions and molecules that contribiute to the main spectral features from 0.5 to 12 mum. Furthermore, we demonstrate the effect on the individual spectral features due to the carbon depletion when dust is formed in the atmosphere.

A&A 342, 531