R. Loidl 1, B. Aringer 1, J. Hron 1, F. Kerschbaum 1, S. Höfner 1,2, U.G. Jørgensen 2, & W. Windsteig 2
1 Institut für Astronomie, Univ. Vienna, Türkenschanzstraße 17, A-1180 Wien, Austria
2 Niels Bohr Institute, Astronomical Observatory, Juliane Maries Vey 30, DK-2100 Copenhagen, Denmark
The ISO-SWS spectra of several representative carbon- and oxygen-rich AGB variables (RAql, RCas, TDra, VCyg, VCrB and RScl) were obtained at several phases of their pulsational cycle. This allows us to study the molecular features and the dust emission of these objects as a function of stellar parameters as well as pulsational phase.
The observational data are compared with synthetic molecular
spectra based on hydrostatic models (MARCS) and on dynamical
atmospheres, which include such phenomena as pulsation, mass
loss and dust formation. Opacities of CO, CN, C2, C3,
C2H2, HCN, SiO, H2O, TiO, OH and CO2 have been
taken into account. As it turns out, a complete treatment
of molecular opacities including a large number of lines of
species like C3, C2H2, HCN, H2O and TiO is crucial
for the construction of model atmospheres, the interpretation
of dust features and the appearance of the pseudo-continuum.
Some aspects of the SWS spectra like their variations can
only be explained by dynamical atmospheres.
We discuss the influence of the fundamental model parameters
like luminosity, stellar mass, piston velocity and C/O ratio on the
resulting synthetic spectra.
To be able to analyse also the targets with significant mass loss,
we also included a dust component in the synthetic spectra. The dust component
either comes directly from the dynamical models or is modelled with the
DUSTY code. On the basis of these synthetic spectra we also
investigate the influence of molecular features on the interpretation of the
dust emission and vice versa. This is of special importance in the 8 to 16
micron region.
This work was supported by the Austrian Science Fund projects S7308-AST and J1487-PHY. FK is supported by APART (Austrian Academy of Sciences)