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A non-LTE (NLTE) abundance analysis was carried out for three extreme heliumstars (EHes): BD+10 2179, BD-9 4395, and LS IV+6 002, from their opticalspectra with NLTE model atmospheres. NLTE TLUSTY model atmospheres werecomputed with H, He, C, N, O, and Ne treated in NLTE. Model atmosphereparameters were chosen from consideration of fits to observed He I lineprofiles and ionization equilibria of C and N ions. The program SYNSPEC wasthen used to determine the NLTE abundances for Ne as well as H, He, C, N, andO. LTE neon abundances from Ne I lines in the EHes: LSE 78, V1920 Cyg, HD124448, and PV Tel, are derived from published models and an estimate of theNLTE correction applied to obtain the NLTE Ne abundance. We show that thederived abundances of these key elements, including Ne, are well matched withsemi-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 whitedwarf.

Neon and CNO Abundances for Extreme Helium Stars -- A Non-LTE Analysis