Spectroscopic analysis of two CH subgiant stars: HD 50264 and HD 87080

We have compared radii of eclipsing binary components and single stars. We have found a noticeable difference for B0V-G0V components of eclipsing binaries and single stars of the corresponding spectral type. This difference can be confirmed by a reanalysis of results of other published investigations and, in particular, it can explain the disagreement between published scales of bolometric corrections. According to our results, A- and F-type main sequence eclipsing binaries have larger radii and/or higher temperatures than single stars while B-type eclipsing binaries have smaller radii. Possible explanations for these features are proposed. We have concluded that the mass-luminosity relation based on empirical data of eclipsing binary components cannot be used to derive the stellar initial mass function. While our current knowledge of the empirical mass-luminosity relation for masses more than 1.5 m... is based exclusively on eclipsing binaries data, accurate observational data for a few hundred visual binaries of intermediate and high masses should be collected. Then the initial mass function for this mass range should be revised.