Optical interferometry of early-type stars with PAVO@CHARA - I. Fundamental stellar properties

We present interferometric observations of seven main-sequence and three giant stars with spectral types from B2 to F6 using the Precision Astronomical Visible Observations beam combiner at the Center for High Angular Resolution Astronomy array. We have directly determined the angular diameters for these objects with an average precision of 2.3 per cent. We have also computed bolometric fluxes using available photometry in the visible and infrared wavelengths, as well as space-based ultraviolet spectroscopy. Combined with precise Hipparcos parallaxes, we have derived a set of fundamental stellar properties including linear radius, luminosity and effective temperature. Fitting the latter to computed isochrone models, we have inferred masses and ages of the stars. The effective temperatures obtained are in good agreement (at a 3 per cent level) with nearly independent temperature estimations from spectroscopy. They validate recent sixth-order polynomial (B - V) - T_eff empirical relations, but suggest that a more conservative third-order solution could adequately describe the (V - K) - T_eff relation for main-sequence stars of spectral types A0 and later. Finally, we have compared mass values obtained combining surface gravity with inferred stellar radius (gravity mass) and as a result of the comparison of computed luminosity and temperature values with stellar evolutionary models (isochrone mass). The strong discrepancy between isochrone and gravity masses obtained for one of the observed stars, γ Lyr, suggests that determination of the stellar atmosphere parameters should be revised.