Astronomy and Astrophysics, volume 506, 235-244 (2009/10-4)
Accurate fundamental parameters of CoRoT asteroseismic targets. The solar-like stars HD 49933, HD 175726, HD 181420, and HD 181906.
Abstract (from CDS):
The CoRoT satellite has provided high-quality light curves of several solar-like stars. Analysis of these light curves provides oscillation frequencies that make it possible to probe the interior of the stars. However, additional constraints on the fundamental parameters of the stars are important for the theoretical modelling to be successful. We estimate the fundamental parameters (mass, radius, and luminosity) of the first four solar-like targets to be observed in the asteroseismic field. In addition, we determine their effective temperature, metallicity, and detailed abundance patterns. To constrain the stellar mass, radius and age we used the shotgun software, which compares the location of the stars in the Hertzsprung-Russell diagram with theoretical evolution models. This method takes the uncertainties of the observed parameters into account, including the large separation determined from the solar-like oscillations. We determined the effective temperatures and abundance patterns in the stars from the analysis of high-resolution spectra obtained with the HARPS, NARVAL, ELODIE and FEROS spectrographs. We determined the mass, radius, and luminosity of the four CoRoT targets to within 5-10%, 2-4% and 5-13%, respectively. The quality of the stellar spectra determines how well we can constrain the effective temperature. For the two best spectra we get 1-σ uncertainties below 60K and 100-150K for the other two. The uncertainty on the surface gravity is less than 0.08dex for three stars, while it is 0.15dex for HD 181906. The reason for the larger uncertainty is that the spectrum has two components with a luminosity ratio of Lp/Ls=0.50±0.15. While Hipparcos astrometric data strongly suggest it is a binary star, we find evidence that the fainter star may be a background star, since it is less luminous but hotter.
stars: fundamental parameters - binaries: spectroscopic - stars: abundances
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