All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{aah4638f1.eps}\end{figure}$ Figure 1: Sample and average spectra of G 117-B15A (top panel) and its common proper motion companion G 117-B15B (bottom panel). The sample spectrum of G 117-B15A is offset from the mean spectrum by +1.7 mJy while that of G 117-B15B is offset by +2.2 mJy. The average spectra of G 117-B15A and G 117-B15B have been scaled such that the fluxes at $\sim$ 5500 Å correspond to the published V band magnitudes (V= +15.54 and +16.06 respectively).
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4638_f2.eps}\end{figure}$ Figure 2: Light curves constructed from the optical spectra. The times shown are relative to the middle of the time series.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{h4638_f3.eps}\end{figure}$ Figure 3: Fourier Transforms (FTs) of the light curves for data taken in different passbands, with the approximate central wavelengths shown in the top righthand corner of each panel. The top three panels show the FTs from our optical dataset while the lower three show the FTs from archival UV data. The middle curve in each panel shows the residuals after fitting sinusoids with frequencies listed in Table 1. These are offset by -1% in the top three panels, by -1.5% in the next two panels, and by -2.5% in the lowermost panel. The dash-dot-dot-dashed (lowermost) curve in all panels shows the residuals (offset by -1.5% in the top three panels, by -2.5% in the next two panels, and by -4% in the lowermost panel) obtained by including a periodicity at 270.455 s instead of one at 271.95 s (F2). Figure 4 shows an expanded view. Larger residuals result in every case. The positions of F2 and F3 are marked in all panels. Note the differing scales of the vertical axes of the two sets of triplots.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{aah4638f4.eps}\end{figure}$ Figure 4: Expanded view of the Fourier Transforms of the 5500 Å light curve around the region containing F2 and F3. The lower curve in both panels shows the residuals (offset by -0.15%) as obtained by using the periods indicated for F2. The choice of 271.95 s for F2 provides a clearly better fit.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{h4638_f5.eps}\end{figure}$ Figure 5: Fractional wavelength dependent pulsation amplitudes of each of the 3 modes calculated in 5 Å wide bins. The period is indicated next to the name. The observations have been overlaid with model chromatic amplitudes with ${T}_{{\rm eff}}$ = 11.5 kK and $\log g=8$ with ML2/ $\alpha =$ 0.6. Both the observations and the models have been normalised to unity at 5500 Å. The models have been convolved with a Gaussian function (FWHM= 4.4 Å) to emulate a seeing profile. See Sect. 5.1 for details of the parameters used in computing the models.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4638_f6.eps}\end{figure}$ Figure 6: Chromatic phases. The slopes in the continuum phases of F2 and F3 are unexpected. Based on simulations, however, we believe that this might not be intrinsic to the star. This, in contrast to the unexpected deviations from the models of the chromatic amplitudes for F2 (Fig. 5; see text).
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{h4638_f7.eps}\end{figure}$ Figure 7: Expanded view of the chromatic amplitudes and models around H $\beta$ . The top panel shows the strongest mode, F1, overlaid with models having $\ell =1$ and three different effective temperatures, as indicated. The bottom panel shows the same models for $\ell =2$ . The 13.0 kK model fails to match the observations for both $\ell$ values. The $\ell =1$ models are a better match at either of the other two effective temperatures considered than the $\ell =2$ models. This is apparent both in the wings and in the line cores. Note however, that for our grid of models, the 12.25 kK, $\ell =1$ model is a better match in the wings of the lines than the corresponding 11.5 kK model.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{h4638_f8.eps}\end{figure}$ Figure 8: Observed chromatic amplitudes (dots) and synthetic chromatic amplitudes (full line) with noise added and treated in exactly the same way as the data (see Sect. 4 for details).
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{h4638_f9.eps}\end{figure}$ Figure 9: Observed and model chromatic amplitudes for the whole wavelength range. The model shown here is the same as in Fig. 5 i.e. ${T}_{{\rm eff}}$ =11.5 kK, $\log g=8$ , and ML2/ $\alpha =0.6$ . The amplitudes have been normalised to unity at 5500 Å. The horizontal error bars on the ultra-violet amplitudes represent the FWHM of the filters that were used. The vertical line merely serves to emphasise that the optical and ultra-violet observations are not contemporaneous.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4638_f2.eps}\end{figure}$	Figure 2: Light curves constructed from the optical spectra. The times shown are relative to the middle of the time series.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{aah4638f4.eps}\end{figure}$	Figure 4: Expanded view of the Fourier Transforms of the 5500 Å light curve around the region containing F2 and F3. The lower curve in both panels shows the residuals (offset by -0.15%) as obtained by using the periods indicated for F2. The choice of 271.95 s for F2 provides a clearly better fit.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4638_f6.eps}\end{figure}$	Figure 6: Chromatic phases. The slopes in the continuum phases of F2 and F3 are unexpected. Based on simulations, however, we believe that this might not be intrinsic to the star. This, in contrast to the unexpected deviations from the models of the chromatic amplitudes for F2 (Fig. 5; see text).
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8cm,clip]{h4638_f8.eps}\end{figure}$	Figure 8: Observed chromatic amplitudes (dots) and synthetic chromatic amplitudes (full line) with noise added and treated in exactly the same way as the data (see Sect. 4 for details).
Open with DEXTER