THE CLASSIFICATION OF HELIUM-RICH HOT SUBDWARFS

Spectroscopy has been obtained of 23 subluminous stars, twenty of whic h had been classified as ''helium-rich subdwarf B stars'' from 10 Angs trom resolution spectra. From inspection of the He II, He I and Balmer lines, the sample clearly shows a wider range in He II/He I and He/H ratios than hitherto supposed for the class. We introduce a classifica tion scheme for helium-rich hot subdwarfs based on 1.5 Angstrom spectr a of high S/N, which can be extended to include all hot subdwarfs with spectra dominated by H, He I or He II. The aim of this classification scheme is to establish reference standards which would be suitable fo r subsequent fine analysis.