Volume 534, October 2011
|Number of page(s)||4|
|Published online||29 September 2011|
Letter to the Editor
The diameter of the CoRoT target HD 49933
Combining the 3D limb darkening, asteroseismology, and interferometry
Université Nice-Sophia Antipolis, Observatoire de la Côte d’Azur, CNRS UMR
2 Université Nice-Sophia Antipolis, Observatoire de la Côte d’Azur, CNRS UMR 6525, BP 4229, 06304 Nice Cedex, France
3 UCBL/CNRS CRAL, 9 avenue Charles André, 69561 Saint Genis Laval Cedex, France
4 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274, 38041 Grenoble, France
5 CHARA and Department of Physics and Astronomy, Georgia State University, PO Box 4106, Atlanta, GA 30302-4106, USA
6 LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France
7 Georgia State University, PO Box 3969, Atlanta GA 30302-3969, USA
8 CHARA Array, Mount Wilson Observatory, 91023 Mount Wilson CA, USA
9 National Optical Astronomy Observatory, PO Box 26732, Tucson, AZ 85726, USA
Received: 26 May 2011
Accepted: 22 August 2011
Context. The interpretation of stellar pulsations in terms of internal structure depends on the knowledge of the fundamental stellar parameters. Long-base interferometers permit us to determine very accurate stellar radii, which are independent constraints for stellar models that help us to locate the star in the HR diagram.
Aims. Using a direct interferometric determination of the angular diameter and advanced three-dimensional (3D) modeling, we derive the radius of the CoRoT target HD 49933 and reduce the global stellar parameter space compatible with seismic data.
Methods. The VEGA/CHARA spectro-interferometer is used to measure the angular diameter of the star. A 3D radiative hydrodynamical simulation of the surface is performed to compute the limb darkening and derive a reliable diameter from visibility curves. The other fundamental stellar parameters (mass, age, and Teff) are found by fitting the large and small p-mode frequency separations using a stellar evolution model that includes microscopic diffusion.
Results. We obtain a limb-darkened angular diameter of θLD = 0.445 ± 0.012 mas. With the Hipparcos parallax, we obtain a radius of R = 1.42 ± 0.04 R⊙. The corresponding stellar evolution model that fits both large and small frequency separations has a mass of 1.20 ± 0.08 M⊙ and an age of 2.7 Gy. The atmospheric parameters are Teff = 6640 ± 100 K, log g = 4.21 ± 0.14, and [Fe/H] = −0.38.
Key words: stars: oscillations / hydrodynamics / stars: fundamental parameters / techniques: interferometric / asteroseismology / stars: individual: HD 49933
© ESO, 2011
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