All Figures

$\begin{figure} \par\includegraphics[height=12.3cm,width=6.6cm,angle=-90,clip]{2761fig1.ps}\end{figure}$ Figure 1: EPIC-PN light curve in the 0.2-15 keV range binned in 50 s intervals. High background epochs have been windowed as discussed in the text
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In the text

$\begin{figure} \par\includegraphics[height=8.8cm, width=8.2cm,angle=-90,clip]{2761fig2.ps}\end{figure}$ Figure 2: EPIC-PN power spectra in selected energy ranges. From bottom to top: 0.2-15 keV, 0.2-1 keV, 1-2 keV, 2-5 keV and 5-12 keV. The spin ( $\omega$ ) and harmonics, the beat ( $\omega - \Omega$ ) and the orbital ( $\Omega$ ) frequencies are marked with vertical dotted lines. An enlargment around the spin frequency is shown in the inserted bottom panel where the DFT (solid line) together with the CLEANED spectrum (dashed line) are shown. The spectral window is also shown.
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In the text

$\begin{figure} \par\includegraphics[height=7.4cm,width=7.4cm,clip]{2761fig3a.ps}... ...1.1cm} \includegraphics[height=7.4cm,width=6.9cm,clip]{2761fig3b.ps}\end{figure}$ Figure 3: Left: EPIC-PN folded light curves in selected energy bands at the 515 s period using the ephemeris quoted in the text together with the best sinusoidal fit. Right: the EPIC hardness ratios show no energy dependence of the pulse.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{2761fig4.ps}\end{figure}$ Figure 4: The RXTE spin folded light curves in the 2-6 keV (higher curve) and 6-10 keV (lower curve) bands shown without offset, using Kemp et al. (2002) ephemeris as discussed in the text.
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In the text

$\begin{figure} \par\hspace*{4mm}\includegraphics[height=8cm,width=8cm,clip]{2761fig5a.ps}\includegraphics[height=8cm,width=8cm,clip]{2761fig5b.ps}\end{figure}$ Figure 5: Left: DFTs (solid line) of B and UVW2 time series, together with that using the CLEAN algorithm (dashed line). Right: folded light curves at the 515 s spin period using the X-ray ephemeris quoted in the text. Ordinates are modulation amplitudes.
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In the text

$\begin{figure} \par\hspace*{1.5mm}\includegraphics[height=8cm,width=8cm,clip]{2761fig6a.ps}\includegraphics[height=8cm,width=8cm,clip]{2761fig6b.ps}\end{figure}$ Figure 6: The March 2003 OM B band ( left) and the December 2002 NOT V band ( right) folded light curves at the orbital 85.98 min period after pre-whitening the data from the high frequency spin pulse. Phase zero has an arbitrary origin. Ordinates are modulation amplitudes.
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In the text

$\begin{figure} \par\includegraphics[height=12.5cm,width=6.7cm,angle=-90,clip]{2761fig7.ps}\end{figure}$ Figure 7: The UVBRI NOT light curves together with their best fit sinusoidal function with a period of 515 s. For the B band light curve a polynomial function accounting for the low frequency trend has been included. Ordinates are modulation amplitudes.
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In the text

$\begin{figure} \par\includegraphics[height=8cm,width=8cm,clip]{2761fig8a.ps}\includegraphics[height=8cm,width=8cm,clip]{2761fig8b.ps}\end{figure}$ Figure 8: Left: the DFTs of UBVRI light curves show a that the spin pulse is present in all bands except in the U. Right: folded light curves at the 515 s period using Kemp et al. (2002) ephemeris. These confirm the lack of UV pulsation but a strong optical modulation at longer wavelengths. Ordinates are modulation amplitudes.
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In the text

$\begin{figure} \par\includegraphics[height=14cm,width=7cm,angle=-90,clip]{2761fig9.ps}\end{figure}$ Figure 9: The EPIC PN ( top) and combined MOS ( bottom) spectra fitted simultaneously with a multi-temperature model with ${\it kT}_{\rm max}$ = 19 keV and power law index $\alpha$ = 0.72 absorbed by a column with density $N_{\rm H}=5.9$ $\times$ 10²⁰ cm^-2 plus a Gaussian centred at 6.4 keV to account for the fluorescent iron line. The bottom panel shows the residuals.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{2761fig10.ps}\end{figure}$ Figure 10: The region including the oxygen lines of the RGS spectra, together with the EPIC best fit model. The rest wavelengths of the lines are also marked. The positions for the forbidden (f), intercombination (i) and resonance (r) lines are displayed.
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In the text

$\begin{figure} \par\includegraphics[height=12.3cm,width=6.6cm,angle=-90,clip]{2761fig1.ps}\end{figure}$	Figure 1: EPIC-PN light curve in the 0.2-15 keV range binned in 50 s intervals. High background epochs have been windowed as discussed in the text
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$\begin{figure} \par\includegraphics[height=7.4cm,width=7.4cm,clip]{2761fig3a.ps}... ...1.1cm} \includegraphics[height=7.4cm,width=6.9cm,clip]{2761fig3b.ps}\end{figure}$	Figure 3: Left: EPIC-PN folded light curves in selected energy bands at the 515 s period using the ephemeris quoted in the text together with the best sinusoidal fit. Right: the EPIC hardness ratios show no energy dependence of the pulse.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{2761fig4.ps}\end{figure}$	Figure 4: The RXTE spin folded light curves in the 2-6 keV (higher curve) and 6-10 keV (lower curve) bands shown without offset, using Kemp et al. (2002) ephemeris as discussed in the text.
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$\begin{figure} \par\hspace*{4mm}\includegraphics[height=8cm,width=8cm,clip]{2761fig5a.ps}\includegraphics[height=8cm,width=8cm,clip]{2761fig5b.ps}\end{figure}$	Figure 5: Left: DFTs (solid line) of B and UVW2 time series, together with that using the CLEAN algorithm (dashed line). Right: folded light curves at the 515 s spin period using the X-ray ephemeris quoted in the text. Ordinates are modulation amplitudes.
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$\begin{figure} \par\hspace*{1.5mm}\includegraphics[height=8cm,width=8cm,clip]{2761fig6a.ps}\includegraphics[height=8cm,width=8cm,clip]{2761fig6b.ps}\end{figure}$	Figure 6: The March 2003 OM B band ( left) and the December 2002 NOT V band ( right) folded light curves at the orbital 85.98 min period after pre-whitening the data from the high frequency spin pulse. Phase zero has an arbitrary origin. Ordinates are modulation amplitudes.
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$\begin{figure} \par\includegraphics[height=12.5cm,width=6.7cm,angle=-90,clip]{2761fig7.ps}\end{figure}$	Figure 7: The UVBRI NOT light curves together with their best fit sinusoidal function with a period of 515 s. For the B band light curve a polynomial function accounting for the low frequency trend has been included. Ordinates are modulation amplitudes.
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$\begin{figure} \par\includegraphics[height=8cm,width=8cm,clip]{2761fig8a.ps}\includegraphics[height=8cm,width=8cm,clip]{2761fig8b.ps}\end{figure}$	Figure 8: Left: the DFTs of UBVRI light curves show a that the spin pulse is present in all bands except in the U. Right: folded light curves at the 515 s period using Kemp et al. (2002) ephemeris. These confirm the lack of UV pulsation but a strong optical modulation at longer wavelengths. Ordinates are modulation amplitudes.
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$\begin{figure} \par\includegraphics[height=14cm,width=7cm,angle=-90,clip]{2761fig9.ps}\end{figure}$	Figure 9: The EPIC PN ( top) and combined MOS ( bottom) spectra fitted simultaneously with a multi-temperature model with ${\it kT}_{\rm max}$ = 19 keV and power law index $\alpha$ = 0.72 absorbed by a column with density $N_{\rm H}=5.9$ $\times$ 10²⁰ cm^-2 plus a Gaussian centred at 6.4 keV to account for the fluorescent iron line. The bottom panel shows the residuals.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{2761fig10.ps}\end{figure}$	Figure 10: The region including the oxygen lines of the RGS spectra, together with the EPIC best fit model. The rest wavelengths of the lines are also marked. The positions for the forbidden (f), intercombination (i) and resonance (r) lines are displayed.
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