Determining Parameters of Cool Giant Stars by Modeling Spectrophotometric and Interferometric Observations Using the SAtlas Program

Abstract

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, ψPhoenicis, γSagittae, and αCeti. The best-fit parameters are compared with previous results. Results: The best-fit angular diameters and values of χ^2 are consistent with predictions using Phoenix and plane-parallel Atlas models. The predicted effective temperatures, using SAtlas, are about 100 to 200 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 ψPhe differs slightly, although both agree within the uncertainty of the interferometric observations.

5 pages, 6 figures, Accepted for publication in A&A as a Research Note

References in corpus (5)

• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• The NextGen Model Atmosphere grid: II. Spherically symmetric model atmospheres for giant stars with effective temperatures between 3000 and 6800~K
• Tests of stellar model atmospheres by optical interferometry: VLTI/VINCI limb-darkening measurements of the M4 giant psi phe
• Tests of stellar model atmospheres by optical interferometry IV: VINCI interferometry and UVES spectroscopy of Menkar
• Tests of stellar model atmospheres by optical interferometry III: NPOI and VINCI interferometry of the M0 giant gamma Sge covering 0.5 - 2.2 microns

Cited by in corpus (13)

• ULySS: A Full Spectrum Fitting Package
• Cepheid distances from the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS) - Application to the prototypes delta Cep and eta Aql
• Comparative Modelling of the Spectra of Cool Giants
• Spherically-symmetric model stellar atmospheres and limb darkening I: limb-darkening laws, gravity-darkening coefficients and angular diameter corrections for red giant stars
• SAtlas: Spherical Versions of the Atlas Stellar Atmosphere Program
• Cepheid limb darkening, angular diameter corrections, and projection factor from static spherical model stellar atmospheres
• Determination of stellar parameters of C-rich hydrostatic stars from spectro-interferometric observations
• Modelling the atmosphere of the carbon-rich Mira RU Vir
• Catching the fish - Constraining stellar parameters for TX Psc using spectro-interferometric observations
• Using limb darkening to measure fundamental parameters of stars
• Stellar atmospheres, atmospheric extension and fundamental parameters: weighing stars using the stellar mass index
• Limb Darkening and Planetary Transits II: Intensity profile correction factors for a grid of model stellar atmospheres
• Comparison of limb-darkening laws from plane-parallel and spherically-symmetric model stellar atmospheres