Josef Hron, Bernhard Aringer, Franz Kerschbaum, Thomas Lebzelter, Walter Nowotny, Thomas Posch, Michael Lederer, Hannes Richter, Susanne Höfner, Rita Gautschy-Loidl, and Tijl Verhoelst
THE MANY FACES OF RED GIANTS (Poster)

THE MANY FACES OF RED GIANTS

Josef Hron(1), Bernhard Aringer(1), Franz Kerschbaum(1), Thomas Lebzelter(1), Walter Nowotny(1), Thomas Posch(1), Michael Lederer(1), Hannes Richter(1), Susanne Höfner(2), Rita Gautschy-Loidl(3), and Tijl Verhoelst(4)
(1)Institut für Astronomie, Universität Wien,
Türkenschanzstr. 17, A-1180 Vienna, Austria
hron@astro.univie.ac.at
(2)Department of Astronomy and Space Physics, Uppsala University,
Uppsala, Sweden
(3)Basel, Switzerland
(4)Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Belgium

Research on the astrophysics of red giants started in Vienna in the mid 1980s. Infrared astronomy of course played a crucial role in these efforts. Equally important were the development and continuous improvement of dynamic model atmospheres yielding synthetic spectra and visibilities. In this poster we summarize highlights of the past work and present some of the latest results.

Systematic comparisons of ISO-SWS spectra with hydrostatic and dynamic models have shown that stars with small variability can be rather well reproduced with static models while dynamic models are needed for stars with larger amplitudes. For C-stars there is rather good agreement between models and observations out to about 7$\mu$m but there is a remarkable discrepancy in the N-band in the sense that a very deep C$_2$H$_2$ absorption predicted by the models is basically never observed.

Analysing an extensive set of ground based high-resolution IR-spectra the common characteristics of the atmospheric motions in Miras and the differences to Semiregular variables could be well established.

Using ISO-SWS data of O-rich AGB-stars in combination with laboratory measurements of various dust species the possible carriers of features at 13$\mu$m and 19.5$\mu$m were identified. In view of future far-IR observations of circumstellar shells with HERSCHEL, we are currently investigating the optical properties of astrophysically relevant solids at wavelengths longer than 57$\mu$m.

Recent results presented in the poster concern the atmospheric dynamics, elemental abundances and dust mineralogy of AGB-stars in galactic and extragalactic globular clusters using ground based IR-spectrometers and the Spitzer-IRS.

We also discuss the atmospheric motions and the atmospheric structure of nearby carbon-rich giants investigated with FTS-spectra and MIDI at the VLTI.