Title: Fundamental Parameters and the Helium Content of Eclipsing Spectroscopic Binaries
Abstract: Today we know accurate masses, radii, surface gravities and luminosities or effective temperatures of a very small number of stars. There are several reasons for deriving accurate parameters of stars. I shall mention only four problems: (i) checking stellar evolution calculations, particularly calculations of isochrones, using binaries, (ii) derivation of helium content in stars of different age, (iii) checking log g derived from photometry and stellar atmosphere calculations, (iv) determination of accurate positions in the HR diagram to get an independent check on calibrations of photometric systems.