EDP Sciences
Free access
Volume 412, Number 2, December III 2003
Page(s) 481 - 494
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20031430

A&A 412, 481-494 (2003)
DOI: 10.1051/0004-6361:20031430

Optical and near-IR spectra of O-rich Mira variables: A comparison between models and observations

A. Tej1, A. Lançon1, M. Scholz2 and P. R. Wood3

1  Observatoire Astronomique de Strasbourg, Université L. Pasteur & CNRS (UMR 7550), Strasbourg, France
    e-mail: surname@astro.u-strasbg.fr
2  Institut f. Theoretische Astrophysik der Universität Heidelberg, Tiergartenstr. 15, 69121 Heidelberg, Germany and School of Physics, University of Sydney, NSW 2006, Australia
    e-mail: scholz@ita.uni-heidelberg.de
3  Research School for Astronomy and Astrophysics, Australian National University, Canberra ACT 2600, Australia
    e-mail: wood@mso.anu.edu.au

(Received 26 February 2003 / Accepted 3 September 2003)

Pulsation models are crucial for the interpretation of spectrophotometric and interferometric observations of Mira variables. Comparing predicted and observed spectra is one way of establishing the validity of such models. In this paper, we focus on the models published between 1996 and 1998 by Bessell, Hofmann, Scholz and Wood. A few new model spectra are added, to improve available phase coverage. We compare the synthetic spectra with observed low resolution spectra of optically selected oxygen-rich Miras, over a range of optical and near-IR wavelengths that encompasses most of the stellar energy output. We investigate the overall energy distributions, and specific spectral features in the near-IR wavelength range. The agreement between the observed and the model-predicted properties is found to be reasonably good. However, there are discrepancies seen especially in various molecular bands. We find that different combinations of stellar parameters and pulsation phases often result in very similar model spectra.

Therefore the problem of deriving parameters of a Mira variable from its spectrum has no unique solution. More advanced models than presently available, providing even better fits to the data and covering a wider range of parameters, would be needed to achieve better discrimination.

Key words: stars: atmospheres -- stars: fundamental parameters -- stars: late-type -- stars: variables: general

Offprint request: A. Lançon, lancon@astro.u-strasbg.fr

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