All Figures

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f1.ps} \end{figure}$ Figure 1: Amplitude spectrum of PG 1657+416 obtained with the NOT in May, 2004 (discovery run, upper panel) and that obtained with the NOT in June, 2004 (confirmation run, lower panel). The continuous horizontal lines indicate 3.7 times the noise level (in amplitude), the dashed lines indicate 3 times the noise level.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f2.ps} \end{figure}$ Figure 2: Upper: light curve of PG 1657+416 obtained with the IAC80 telescope in May, 2005; Middle: light curve obtained with the NOT in May, 2005; Bottom: detail of the light curve obtained with the NOT and the fit to a synthetic light curve (in red), computed from the frequencies derived from these data, and listed in Table 3.
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{5119f3.ps} \end{figure}$ Figure 3: Run: IAC80 May, 2005. From top to bottom: spectral window, amplitude spectrum, and those after successively subtracting peaks from the signal. The continuous horizontal line indicates 3.7 times the noise level, whereas the dashed one corresponds to 3 times this level. The vertical dashed lines mark the frequencies that are removed during the prewhitening process.
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{5119f4.ps} \end{figure}$ Figure 4: Run: NOT May, 2005. From top to bottom: spectral window, amplitude spectrum, and those after successively subtracting peaks from the signal. The continuous horizontal line indicates 3.7 times the noise level, whereas the dashed one corresponds to 3 times this level. The vertical dashed lines mark the frequencies that are removed during the prewhitening process.
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{5119f5.ps} \end{figure}$ Figure 5: Run: IAC80+NOT 2005. From top to bottom: spectral window, amplitude spectrum, and those after successively subtracting peaks from the signal. The continuous horizontal line indicates 3.7 times the noise level, the dashed one corresponds to 3 times the noise. The vertical dashed lines mark the frequencies that are removed during the prewhitening process.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{5119f6.ps} \end{figure}$ Figure 6: Observed spectrum, 2MASS magnitudes converted to fluxes (asterisks) and the best fit to a sum of two Kurucz model atmospheres obtained by adding a spectrum with $T_{\rm eff}=5500$ and $\log g=4$ to a sdB model with $T_{\rm eff}=34~000$ and $\log g=5$ .
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{5119f7.ps} \end{figure}$ Figure 7: Best line fit to the observed flux after subtracting a main sequence $T_{\rm eff}=5500$ K model atmosphere.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5119f8.ps} \end{figure}$ Figure 8: $\log g{-}T_{\rm eff}$ diagram in which three sdB evolutionary sequences (A, B, C) produced by a complete evolution from a main sequence star are displayed. Sequence D was artificially generated so that it has a higher total mass and crosses the star's location at an earlier evolutionary stage. Some ages (in 10⁸ years) are given at the points indicated with asterisks. The values of $\log g{-}T_{\rm eff}$ obtained in the previous section for PG 1657+416 are indicated with a dashed error box.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f9.ps} \end{figure}$ Figure 9: Theoretical frequencies for structural models of sequences A, B, C and D. The y-axis indicates the age of the models, while the vertical broken lines point out the observed frequencies. Crosses: modes with $\ell =0$ ; asterisks: models with $\ell =1$ ; rhombus: $\ell =2$ ; triangles: $\ell =3$ .
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f10.ps} \end{figure}$ Figure 10: The frequency separation $\Delta \nu _{0,2} \equiv \nu _{\ell =0}-\nu _{\ell =2}$ (crosses), $\Delta \nu _{3,0}$ (triangles) and $\Delta \nu _{1,3}$ (asterisks) for structural models from sequence A, B, C and D. The values of f₂-f₄=0.101 mHz and f₄-f₃=0.163 mHz are overplotted as horizontal broken lines for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{5119f11.ps} \end{figure}$ Figure 11: Frequency separation between modes of consecutive radial order for $\ell =0$ (crosses), 1 (asterisks), 2 (rhombus) and 3 (triangles) as a function of time for the four sequences. The observed frequency separation f₂-f₁=0.94 mHz is overplotted as an horizontal broken line for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f1.ps} \end{figure}$	Figure 1: Amplitude spectrum of PG 1657+416 obtained with the NOT in May, 2004 (discovery run, upper panel) and that obtained with the NOT in June, 2004 (confirmation run, lower panel). The continuous horizontal lines indicate 3.7 times the noise level (in amplitude), the dashed lines indicate 3 times the noise level.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f2.ps} \end{figure}$	Figure 2: Upper: light curve of PG 1657+416 obtained with the IAC80 telescope in May, 2005; Middle: light curve obtained with the NOT in May, 2005; Bottom: detail of the light curve obtained with the NOT and the fit to a synthetic light curve (in red), computed from the frequencies derived from these data, and listed in Table 3.
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$\begin{figure} \par\includegraphics[width=6.8cm,clip]{5119f3.ps} \end{figure}$	Figure 3: Run: IAC80 May, 2005. From top to bottom: spectral window, amplitude spectrum, and those after successively subtracting peaks from the signal. The continuous horizontal line indicates 3.7 times the noise level, whereas the dashed one corresponds to 3 times this level. The vertical dashed lines mark the frequencies that are removed during the prewhitening process.
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$\begin{figure} \par\includegraphics[width=6.8cm,clip]{5119f4.ps} \end{figure}$	Figure 4: Run: NOT May, 2005. From top to bottom: spectral window, amplitude spectrum, and those after successively subtracting peaks from the signal. The continuous horizontal line indicates 3.7 times the noise level, whereas the dashed one corresponds to 3 times this level. The vertical dashed lines mark the frequencies that are removed during the prewhitening process.
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$\begin{figure} \par\includegraphics[width=6.8cm,clip]{5119f5.ps} \end{figure}$	Figure 5: Run: IAC80+NOT 2005. From top to bottom: spectral window, amplitude spectrum, and those after successively subtracting peaks from the signal. The continuous horizontal line indicates 3.7 times the noise level, the dashed one corresponds to 3 times the noise. The vertical dashed lines mark the frequencies that are removed during the prewhitening process.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{5119f6.ps} \end{figure}$	Figure 6: Observed spectrum, 2MASS magnitudes converted to fluxes (asterisks) and the best fit to a sum of two Kurucz model atmospheres obtained by adding a spectrum with $T_{\rm eff}=5500$ and $\log g=4$ to a sdB model with $T_{\rm eff}=34~000$ and $\log g=5$ .
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$\begin{figure} \par\includegraphics[width=7cm,clip]{5119f7.ps} \end{figure}$	Figure 7: Best line fit to the observed flux after subtracting a main sequence $T_{\rm eff}=5500$ K model atmosphere.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f9.ps} \end{figure}$	Figure 9: Theoretical frequencies for structural models of sequences A, B, C and D. The y-axis indicates the age of the models, while the vertical broken lines point out the observed frequencies. Crosses: modes with $\ell =0$ ; asterisks: models with $\ell =1$ ; rhombus: $\ell =2$ ; triangles: $\ell =3$ .
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5119f10.ps} \end{figure}$	Figure 10: The frequency separation $\Delta \nu _{0,2} \equiv \nu _{\ell =0}-\nu _{\ell =2}$ (crosses), $\Delta \nu _{3,0}$ (triangles) and $\Delta \nu _{1,3}$ (asterisks) for structural models from sequence A, B, C and D. The values of f₂-f₄=0.101 mHz and f₄-f₃=0.163 mHz are overplotted as horizontal broken lines for comparison.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{5119f11.ps} \end{figure}$	Figure 11: Frequency separation between modes of consecutive radial order for $\ell =0$ (crosses), 1 (asterisks), 2 (rhombus) and 3 (triangles) as a function of time for the four sequences. The observed frequency separation f₂-f₁=0.94 mHz is overplotted as an horizontal broken line for comparison.
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