  A non-LTE (NLTE) abundance analysis was carried out for three extreme helium
stars (EHes): BD+10 2179, BD-9 4395, and LS IV+6 002, from their optical
spectra with NLTE model atmospheres. NLTE TLUSTY model atmospheres were
computed with H, He, C, N, O, and Ne treated in NLTE. Model atmosphere
parameters were chosen from consideration of fits to observed He I line
profiles and ionization equilibria of C and N ions. The program SYNSPEC was
then used to determine the NLTE abundances for Ne as well as H, He, C, N, and
O. LTE neon abundances from Ne I lines in the EHes: LSE 78, V1920 Cyg, HD
124448, and PV Tel, are derived from published models and an estimate of the
NLTE correction applied to obtain the NLTE Ne abundance. We show that the
derived abundances of these key elements, including Ne, are well matched with
semi-quantitative predictions for the EHe resulting from a cold merger (i.e.,
no nucleosynthesis during the merger) of a He white dwarf with a C-O white
dwarf.
