Calibrating horizontal-branch stars with Hipparcos ?

Parallaxes from the Hipparcos satellite allow for the rst time to calibrate parameters of horizontal-branch (HB) like stars based on geometric distances. We present absolute mag- nitudes and luminosities for 8 such stars. Using Teff and log g values available from the literature, we also can calculate the mass of the HB stars. We nd an average value of MHB = 0.38 0:07 M for stars with 7500 stellar evolution theory, which predicts masses near 0.6 M. Recent investigations of HB stars in globular clusters indicated similarly low mass values. The likely cause for the discrepancy of the mass values lies in the low gravities derived from Balmer line proles.