2011A&A...534L...3B

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. Using a direct interferometric determination of the angular diameter and advanced three-dimensional (3D) modeling, we derive the radius of the CoRoT target HD49933 and reduce the global stellar parameter space compatible with seismic data. 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 T_eff) are found by fitting the large and small p-mode frequency separations using a stellar evolution model that includes microscopic diffusion. We obtain a limb-darkened angular diameter of θ_LD=0.445±0.012mas. With the Hipparcos parallax, we obtain a radius of R=1.42±0.04R_☉. The corresponding stellar evolution model that fits both large and small frequency separations has a mass of 1.20±0.08M_☉ and an age of 2.7Gy. The atmospheric parameters are T_eff=6640±100K, logg=4.21±0.14, and [Fe/H]=-0.38.