EDP Sciences
Free access
Volume 490, Number 2, November I 2008
Page(s) 807 - 810
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:200810627
Published online 17 September 2008

A&A 490, 807-810 (2008)
DOI: 10.1051/0004-6361:200810627

Research Note

Determining parameters of cool giant stars by modeling spectrophotometric and interferometric observations using the SATLAS program

H. R. Neilson1 and J. B. Lester2

1  Department of Astronomy & Astrophysics, University of Toronto, Canada
    e-mail: neilson@astro.utoronto.ca
2  Department of Chemical and Physical Sciences, University of Toronto Mississauga, Canada
    e-mail: lester@astro.utoronto.ca

Received 16 July 2008 / Accepted 12 September 2008

Context. Optical interferometry is a powerful tool for observing the intensity structure and angular diameter of stars. When combined with spectroscopy and/or spectrophotometry, interferometry provides a powerful constraint for model stellar atmospheres.
Aims. The purpose of this work is to test the robustness of the spherically symmetric version of the ATLAS stellar atmosphere program, SATLAS, using interferometric and spectrophotometric observations.
Methods. Cubes (three dimensional grids) of model stellar atmospheres, with dimensions of luminosity, mass, and radius, are computed to fit observations for three evolved giant stars, $\psi$ Phoenicis, $\gamma$ Sagittae, and $\alpha$ Ceti. The best-fit parameters are compared with previous results.
Results. The best-fit angular diameters and values of $\chi^2$ are consistent with predictions using PHOENIX and plane-parallel ATLAS models. The predicted effective temperatures, using SATLAS, are about 100 to 200 $\rm {K}$ lower, and the predicted luminosities are also lower due to the differences in effective temperatures.
Conclusions. It is shown that the SATLAS program is a robust tool for computing models of extended stellar atmospheres that are consistent with observations. The best-fit parameters are consistent with predictions using PHOENIX models, and the fit to the interferometric data for $\psi$ Phe differs slightly, although both agree within the uncertainty of the interferometric observations.

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

© ESO 2008