All Figures

$\begin{figure} \par\includegraphics[angle=-90,scale=0.42]{3399fig1.eps}\end{figure}$ Figure 1: Top: zoomed trailed spectrogram of the H $\beta$ line around eclipse. Bright regions are dark. Bottom: the integrated line profile along the eclipse phases of the spectrogram on the top panel (from $\phi = -0.1$ to +0.1 cycle). Vertical dotted lines mark the two velocity-resolved regions used to extract light curves of the spiral arms and to isolate low-velocity emitting gas.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=14cm]{3399fig2.eps}\end{figure}$ Figure 2: Extracted core ( left panels) and spiral ( right panels) light curves for He II and H $\beta$ (in black) and for He I and the Bowen blend (in grey). Vertical dotted lines mark mid-ingress/egress phases of the white dwarf and the reference phases -0.1 and +0.1 cycles. The light curves are repeated in phase for visualization purposes. The H $\gamma$ light curves (not shown) are very similar to those of H $\beta$ .
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In the text

$\begin{figure} \par\includegraphics[width=14cm]{3399fig3.eps}\end{figure}$ Figure 3: Left: data trailed spectrograms (linear greyscale) and corresponding Doppler maps (logarithmic greyscale) for H $\beta$ , He II 4686, the Bowen blend, He I 4472, and H $\gamma$ . Dark regions are brighter. A cross marks the position of the white dwarf. Dotted lines outline the Roche lobe of the secondary star and the velocities along the ballistic stream trajectory. Right: line spiral light curves and corresponding eclipse maps on a logarithmic greyscale. Dark regions are brighter. The bar in the right side indicates the greyscale used in each case. Dotted lines show the primary Roche lobe and a circle of radius $0.6 \;R_{L1}$ . A cross marks the centre of the disc. The secondary is to the right of each panel and the stars rotate counter-clockwise. A solid contour line is overploted on each eclipse map to indicate the 3- $\sigma$ confidence level region.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=13.5cm]{3399fig4.eps}\end{figure}$ Figure 4: The dependency with binary phase of the maximum intensity (lowermost panels), radius and corresponding Keplerian velocity at maximum intensity (second and third rows of panels from the bottom) as derived from the line eclipse maps. Dotted lines depict the $\pm 1 \sigma$ limits in these distributions. The velocities were computed assuming $M_1= 1.02\;M_\odot$ and $R_{L1}= 0.81\;R_\odot$ (Marsh & Horne 1990), and the intensities are plotted in an arbitrary scale. The orbital dependency of the Doppler velocity of maximum intensity (extracted from the Doppler maps of Fig. 3) is shown as a solid grey line in the velocity panels. The location of the spiral arms are indicated in the lowermost panels by horizontal bars labeled "blue'' (outer spiral) and "red'' (inner spiral). Vertical dotted lines in the lowermost panels mark the phase of minimum intensity of the valley in between the spirals and are used to estimate the spirals opening angle (see Sect. 4). The uppermost panels show the ratio of the observed velocity (Doppler map) to the Keplerian velocity at the same radius (eclipse map). A horizontal dashed line in each panel depicts the reference unity velocity ratio.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{3399fig5.eps}\end{figure}$ Figure 5: The measured opening angle of the spiral arms in IP Peg as a function of outburst stage.
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In the text

$\begin{figure}\par\includegraphics[width=8.5cm]{3399apf1.eps}\end{figure}$ Figure A.1: Comparison of reconstructions obtained with the standard eclipse mapping (single default map) and the double-default eclipse mapping. The top panel shows the original map with two spiral arms of opening angle $\phi =30^\circ$ in a logarithmic greyscale. The left panels depict the simulated data (dots with error bars) and model light curves (solid lines) in each case. Vertical dotted lines indicate the phases of mid-eclipse and of ingress/egress of the disc centre. The right panels show the reconstructions obtained with the standard eclipse mapping ( middle panel) and with the double default mapping ( lower panel) in the same logarithmic greyscale. The notation is similar to that of Fig. 3.

In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{3399apf2.eps}\end{figure}$ Figure A.2: Sequence of brightness distributions with spiral arms of different opening angles. Left panel: simulated noisy light curves ( ${\it S/N}=50$ , gray dots with error bars) and eclipse mapping model light curves (solid lines). Vertical dotted lines mark the ingress and egress phases of the disc centre. Middle panels: original maps ( left) and eclipse mapping reconstructions with the double-default map ( right). The reconstructions were obtained with $\Delta \theta = 10^\circ$ . The notation is similar to that of Fig. A.1. Right panels: the azimuthal dependency of the maximum intensity of the original maps (dashed line) and of the reconstructions (solid line). Vertical dotted lines mark the azimuths of minimum light in each case.

In the text

$\begin{figure} \par\includegraphics[width=8.3cm]{3399apf3.eps}\end{figure}$ Figure A.3: Reconstruction of a brightness distribution with spiral arms of $\phi =15^\circ$ and radial range 0.3-0.55 R_L1. Top: original ( left) and reconstructed ( right) maps. Bottom: the azimuthal dependency of the maximum intensity of the original map (dashed line) and of the reconstruction (solid line). The notation is the same as in Fig. A.2.

In the text

$\begin{figure} \par\includegraphics[angle=-90,scale=0.42]{3399fig1.eps}\end{figure}$	Figure 1: Top: zoomed trailed spectrogram of the H $\beta$ line around eclipse. Bright regions are dark. Bottom: the integrated line profile along the eclipse phases of the spectrogram on the top panel (from $\phi = -0.1$ to +0.1 cycle). Vertical dotted lines mark the two velocity-resolved regions used to extract light curves of the spiral arms and to isolate low-velocity emitting gas.
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$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{3399fig5.eps}\end{figure}$	Figure 5: The measured opening angle of the spiral arms in IP Peg as a function of outburst stage.
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