which have much fainter observed UIT magnitudes than predicted. A possible cause for these discrepancies might be the omission of carbon or other metal opacity in our model atmospheres, which Lanz et al. ([@labr03]) have shown can affect both the derived atmospheric parameters from optical spectra, and the ultraviolet flux distribution.

[psfile=0505\_7.ps hscale=42 vscale=42 hoffset=-0 voffset=-70 angle=0]{}

Carbon abundances
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Along with a large helium enhancement, the flash-mixing scenario also predicts a strong surface carbon enhancement. The flash-mixed model computed by Cassisi et al. ([@casc03]) is strongly enhanced in both carbon (mass fraction 0.029) and nitrogen (mass fraction 0.007). The corresponding solar mass fractions are 0.0028 and 0.00081 for C and N, respectively. We see lines of $\lambda\lambda$ 4070, 4170, 4650 Å in several of our spectra, but our low resolution and S/N prevents a detailed abundance analysis.

To obtain a rough estimate of the carbon abundance, we began with the H-He NLTE models used to derive Teff, log g and the helium abundance. Keeping these parameters fixed we then computed five additional models with CNO[^3] logarithmic mass fractions relative to solar of $-1.5$, $-0.5$, $0.0$, $+0.5$, and $+1.0$. As noted by Lanz et al. ([@labr03]), this approach is inconsistent 