All Figures

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{4221fig1.eps}\end{figure}$ Figure 1: IUE spectra obtained for Feige 4 (full line) compared with the best models derived leaving all parameters free for a pure He grid (dashed line) at d=61 pc, with $T_{{\rm eff}}=19~000$ K and $\log g=8.50$ , for a a DB contaminated with H (dotted line), at d=112 pc, with $T_{{\rm eff}}=18~000$ K and $\log g=7.50$ . Using the parallax distance, (d=33 pc) for pure He grid (dotted-dashed line), the best solution is for $T_{{\rm eff}}=14~000$ K and $\log g=8.50$ , and for a DB contaminated with H (long dashed line), the atmospheric parameters are $T_{{\rm eff}}=17~000$ K and $\log g=9.00$ .
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{4221fig2.eps} \end{figure}$ Figure 2: Comparison between the UV (x-axis) and optical (y-axis) determinations for $T_{{\rm eff}}$ using pure He models (blue triangles) and DB models contaminated with H (red squares). The dotted lines correspond to the same star. The dashed line delineates 1:1 correspondence between UV and optical spectra.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4221fig3.eps} \end{figure}$ Figure 3: Fourier amplitude spectra of the null results of a search for pulsation among DB white dwarf stars.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{4221fig4.eps}\end{figure}$ Figure 4: DB instability strip using pure He models for the stars for which we cannot determine atmosphere composition: variables (filled triangle), non-variables (filled squares), and not observed for variability (open circles). There are 2 stars close to the instability strip that have not been observed for variability.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4221fig5.eps} \end{figure}$ Figure 5: DB instability strip using H contaminated He models for the stars for which we cannot determine atmosphere composition: variables (filled triangle), non-variables (filled squares), and not observed for variability (open circles). There are 2 stars close to the instability strip that have not been observed for variability.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{4221fig2.eps} \end{figure}$	Figure 2: Comparison between the UV (x-axis) and optical (y-axis) determinations for $T_{{\rm eff}}$ using pure He models (blue triangles) and DB models contaminated with H (red squares). The dotted lines correspond to the same star. The dashed line delineates 1:1 correspondence between UV and optical spectra.
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$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4221fig3.eps} \end{figure}$	Figure 3: Fourier amplitude spectra of the null results of a search for pulsation among DB white dwarf stars.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{4221fig4.eps}\end{figure}$	Figure 4: DB instability strip using pure He models for the stars for which we cannot determine atmosphere composition: variables (filled triangle), non-variables (filled squares), and not observed for variability (open circles). There are 2 stars close to the instability strip that have not been observed for variability.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4221fig5.eps} \end{figure}$	Figure 5: DB instability strip using H contaminated He models for the stars for which we cannot determine atmosphere composition: variables (filled triangle), non-variables (filled squares), and not observed for variability (open circles). There are 2 stars close to the instability strip that have not been observed for variability.
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