EDP Sciences
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Volume 437, Number 1, July I 2005
Page(s) 273 - 284
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20042461

A&A 437, 273-284 (2005)
DOI: 10.1051/0004-6361:20042461

Atmospheric dynamics in carbon-rich Miras

I. Model atmospheres and synthetic line profiles
W. Nowotny1, B. Aringer1, S. Höfner2, R. Gautschy-Loidl3 and W. Windsteig1

1  Institut für Astronomie der Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria
    e-mail: nowotny@astro.univie.ac.at
2  Departement of Astronomy and Space Physics, Uppsala University, Box 515, 75120 Uppsala, Sweden
3  Froburgstrasse 43, 4052 Basel, Switzerland

(Received 1 December 2004 / Accepted 28 February 2005)

Atmospheres of evolved AGB stars are heavily affected by pulsation, dust formation and mass loss, and they can become very extended. Time series of observed high-resolution spectra proved to be a useful tool to study atmospheric dynamics throughout the outer layers of these pulsating red giants. Originating at various depths, different molecular spectral lines observed in the near-infrared can be used to probe gas velocities there for different phases during the lightcycle. Dynamic model atmospheres are needed to represent the complicated structures of Mira variables properly. An important aspect which should be reproduced by the models is the variation of line profiles due to the influence of gas velocities. Based on a dynamic model, synthetic spectra (containing CO and CN lines) were calculated, using an LTE radiative transfer code that includes velocity effects. It is shown that profiles of lines that sample different depths qualitatively reproduce the behaviour expected from observations.

Key words: stars: late-type -- stars: AGB and post-AGB -- stars: atmospheres -- stars: carbon -- infrared: stars -- line: profiles

SIMBAD Objects in preparation

© ESO 2005