  UV observations of some massive globular clusters have revealed a significant
population of stars hotter and fainter than the hot end of the horizontal
branch (HB), the so-called blue hook stars. This feature might be explained
either by the late hot flasher scenario where stars experience the helium flash
while on the white dwarf cooling curve or by the progeny of the helium-enriched
sub-population postulated to exist in some clusters. Previous spectroscopic
analyses of blue hook stars in omega Cen and NGC 2808 support the late hot
flasher scenario, but the stars contain much less helium than expected and the
predicted C and N enrichment cannot be verified. We compare the observed
effective temperatures, surface gravities, helium abundances, and carbon line
strengths (where detectable) of our targets stars with the predictions of the
two aforementioned scenarios. Moderately high resolution spectra of hot HB
stars in the globular cluster omega Cen were analysed for radial velocity
variations, atmospheric parameters, and abundances using LTE and non-LTE model
atmospheres. We find no evidence of close binaries among our target stars. All
stars below 30,000K are helium-poor and very similar to HB stars observed in
that temperature range in other globular clusters. In the temperature range
30,000K to 50,000K, we find that 28% of our stars are helium-poor (log(He/H) <
-1.6), while 72% have roughly solar or super-solar helium abundance (log(He/H)
>= -1.5). We also find that carbon enrichment is strongly correlated with
helium enrichment, with a maximum carbon enrichment of 3% by mass. A strong
carbon enrichment in tandem with helium enrichment is predicted by the late hot
flasher scenario, but not by the helium-enrichment scenario. We conclude that
the helium-rich HB stars in omega Cen cannot be explained solely by the
helium-enrichment scenario invoked to explain the blue main sequence.
