  The connection between helium-rich hot subdwarfs of spectral types O and B
(He-sdB) has been relatively unexplored since the latter were found in
significant numbers in the 1980's. In order to explore this connection further,
we have analysed the surface composition of six He-sdB stars, including LB
1766, LB 3229, SB 21 (= Ton-S 137 = BPS 29503-0009), BPS 22940-0009, BPS
29496-0010, and BPS 22956-0094. Opacity-sampled line-blanketed model
atmospheres have been used to derive atmospheric properties and elemental
abundances. All the stars are moderately metal-poor compared with the Sun
([Fe/H] ~ -0.5). Four stars are nitrogen-rich, two of these are carbon-rich,
and at least four appear to be neon-rich. The data are insufficient to rule out
binarity in any of the sample. The surface composition and locus of the N-rich
He-sdBs are currently best explained by the merger of two helium white dwarfs,
or possibly by the merger of a helium white dwarf with a post-sdB white dwarf.
C-rich He-sdBs require further investigation.

Solar and Stellar Astrophysics