The classification of helium-rich hot subdwarfs

C.S.Jeffery, J.S.Drilling, P.M.Harrison, U.Heber and S.Moehler

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