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Empirical Luminosities and Radii of Early-Type Stars after Hipparcos

Jerzykiewicz M., Molenda-Żakowicz J.

Acta Astronomica

2000

Vol. 50, No. 3

369--380

Using Hipparcos parallaxes we derive empirical luminosities and radii of the early-type stars for which the effective temperatures are known from directly measured angular diameters and total absolute fluxes. The empirical luminosities allow a direct comparison of the position of these stars in the fundamental HR diagram with evolutionary tracks. The comparison shows an overall agreement with the Y=0.30 and Z=0.02 tracks computed with OPAL opacities and moderate amount of overshooting from the convective core. In addition, we present evidence that systematic errors of the masses read off the evolutionary tracks are below 10%. Consequently, the surface gravities obtained from these "evolutionary" masses and the empirical radii are very nearly model-independent. Spectrographic and photometric observations of these stars can therefore be used for verifying model atmospheres and calibrating photometric log g indices.