All Figures

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4283f1.eps} \end{figure}$ Figure 1: Calar Alto image of SBS 0909+532, showing an FOV of $\sim$ $7\hbox {$^\prime $ }\times 7\hbox {$^\prime $ }$ . The field contains the gravitationally lensed quasar ("GL'') and six bright and non-saturated stars ("a-c'', "s1-s2'' and "x''). The nearby ("a-c'') and relatively far ("s1-s2'') field stars were introduced by Kochanek et al. (1997) and Nakos et al. (2003), respectively. A sixth field star ("x'') is also included in the FOV.
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In the text

$\begin{figure} \par\includegraphics[width=4cm,clip]{4283f2.eps} \end{figure}$ Figure 2: Maidanak zoomed-in image of SBS 0909+532 (about 8 $^{\prime \prime }$ on a side). We chose one of the frames taken with the best seeing conditions, and then expanded the portion occupied by the two quasar components A (the brightest object) and B (the faintest object), i.e., the GL in Fig. 1. To avoid the pixellation effect when a subframe is expanded, the brightness distribution is also smoothed.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4283f3.eps} \end{figure}$ Figure 3: $(S/N)_{\rm max}$ versus ${\it FWHM}$ for the Calar Alto frames in the R filter ( top panel) and the V filter ( bottom panel). The circles and triangles represent the frames with good and bad post-fit residues, respectively (see main text).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f4.eps} \end{figure}$ Figure 4: Calar Alto light curves of the double quasar in the R filter. We use the "b'' star as the reference object, because it is confirmed as a non-variable star in Fig. 7. The circles are the fluxes $y_{\rm A}$ ( $y_{\rm A} = m_{\rm A} - m_{\rm b}$ ) and the squares are the fluxes $y_{\rm B} - 0.45$ mag ( $y_{\rm B} = m_{\rm B} - m_{\rm b}$ ). The A light curve has a final decline, while the B light curve ends in a rise.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.8cm,clip]{4283f5.eps} \end{figure}$ Figure 5: Calar Alto light curves of the double quasar in the V filter. We use the non-variable star "b'' as reference object (see Fig. 7). The circles are the fluxes $y_{\rm A}$ and the squares are the fluxes $y_{\rm B} - 0.65$ mag.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f6.eps} \end{figure}$ Figure 6: Calar Alto light curves of the stars in the R filter. The Calar Alto fluxes are checked from six Wise frames. Filled and open symbols are associated with PSF fitting and aperture, respectively. First, the non-variable star "b'' (see Fig. 7) is taken as the reference object. The top box incorporates the behaviour of $y_{\rm a} + 2.15$ mag ( $y_{\rm a} = m_{\rm a} - m_{\rm b}$ ): Calar Alto (open squares) and Wise (open triangles). The second box (under the top box) contains the fluxes $y_{\rm c}$ ( $y_{\rm c} = m_{\rm c} - m_{\rm b}$ ): Calar Alto (filled squares) and Wise (open circles). The third and fourth boxes include the $y_{\rm s1} + 2.38$ mag ( $y_{\rm s1} = m_{\rm s1} - m_{\rm b}$ ) and $y_{\rm s2} + 0.29$ mag ( $y_{\rm s2} = m_{\rm s2} - m_{\rm b}$ ) records, respectively. In the third box: Calar Alto (filled and open triangles) and Wise (open astroids); in the fourth box: Calar Alto (filled and open circles) and Wise (open rhombuses). Second, we plot the $m_{\rm s2} - m_{\rm s1} - 0.20$ mag records in the bottom box: Calar Alto (filled and open star symbols) and Wise (open crosses).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.7cm,clip]{4283f7.eps} \end{figure}$ Figure 7: Maidanak (open star symbols) and Wise (open triangles) light curves $y_{\rm a}$ in the R filter (from late January to the middle of June 2003). The solid line represents the global mean value and the two dashed lines describe the rms fluctuation of the measurements. This rms variation agrees with the typical uncertainty, so "a'' and "b'' seem to be non-variable sources.
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In the text

$\begin{figure} \par\includegraphics[width=6.7cm,clip]{4283f8.eps} \end{figure}$ Figure 8: Global R-band fluxes of SBS 0909+532 in 2003. The open circles (Maidanak) and filled circles (Calar Alto) are the fluxes $y_{\rm A}$ , whereas the open squares (Maidanak) and filled squares (Calar Alto) are the relative fluxes $y_{\rm B} - 0.45$ mag. The top panel contains the results from early February to late May 2003 and the bottom panel includes the results from the middle of October to late November 2003.
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In the text

$\begin{figure} \par\includegraphics[width=6.3cm,clip]{4283f9.eps} \end{figure}$ Figure 9: Galaxy reconstruction obtained from selected Maidanak frames. Although the double quasar has been subtracted here, the positions of the components are labeled with two crosses: A is on the left and B is on the right, and the separation between both crosses is of 1 $.\!\!^{\prime\prime}$ 1-1 $.\!\!^{\prime\prime}$ 2. The galaxy contours cover a region of $10\hbox {$^{\prime \prime }$ }\times 10\hbox {$^{\prime \prime }$ }$ .
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f10.eps} \end{figure}$ Figure 10: $\chi ^2$ spectra for $\alpha = 7$ days (dashed line), $\alpha = 8$ days (solid line), and $\alpha = 9$ days (dotted line). The parameter $\alpha$ is the semiwidth of the bins in the A component, so the three spectra represent different results of a cross-correlation with reasonable time-resolution (the mean sampling time is 6 days/point).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f11.eps} \end{figure}$ Figure 11: $\chi ^2$ spectra for $\alpha = 9$ days (dashed line), $\alpha = 10$ days (solid line), and $\alpha = 11$ days (dotted line), where $\alpha$ is the semiwidth of the bins in the B component.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4283f12.eps} \end{figure}$ Figure 12: Histograms from 1000 repetitions and the $\chi ^2$ minimization (bins in B and $\alpha = 10$ days). Top panel: best solutions of the time delay. Bottom panel: best solutions of the magnitude offset (flux ratio). These distributions are consistent with a delay of about one and a half months and a time-delay-corrected flux ratio of about 0.59 mag.
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{4283f13.eps} \end{figure}$ Figure 13: Comparison between the shifted A light curve (circles) and the B light curve (squares). We use an $\chi ^2$ minimization, bins in B, and $\alpha = 10$ days. Top panel: best solution ( $\Delta \tau _{\rm BA} = - 44$ days, $\Delta m_{\rm BA} = 0.59$ mag). Bottom panel: solution for $\Delta \tau _{\rm BA} = - 80$ days ( $\Delta m_{\rm BA} = 0.56$ mag).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f14.eps} \end{figure}$ Figure 14: Dispersion spectra for $\delta = 7$ days (dashed line), $\delta = 9$ days (solid line), and $\delta = 11$ days (dotted line). The parameter $\delta$ is the decorrelation length associated with the D²_4,2 spectra (Pelt et al. 1996).
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In the text

$\begin{figure} \par\includegraphics[width=6.7cm,clip]{4283f15.eps} \end{figure}$ Figure 15: Histograms from 1000 repetitions and the D² minimization ( $\delta = 9$ days). Top panel: best solutions of the time delay. Bottom panel: best solutions of the magnitude offset (flux ratio). These distributions are again consistent with a 1.5-month delay and and a time-delay-corrected flux ratio of about 0.58-0.59 mag.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4283f3.eps} \end{figure}$	Figure 3: $(S/N)_{\rm max}$ versus ${\it FWHM}$ for the Calar Alto frames in the R filter ( top panel) and the V filter ( bottom panel). The circles and triangles represent the frames with good and bad post-fit residues, respectively (see main text).
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$\begin{figure} \par\includegraphics[angle=-90,width=7.8cm,clip]{4283f5.eps} \end{figure}$	Figure 5: Calar Alto light curves of the double quasar in the V filter. We use the non-variable star "b'' as reference object (see Fig. 7). The circles are the fluxes $y_{\rm A}$ and the squares are the fluxes $y_{\rm B} - 0.65$ mag.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.7cm,clip]{4283f7.eps} \end{figure}$	Figure 7: Maidanak (open star symbols) and Wise (open triangles) light curves $y_{\rm a}$ in the R filter (from late January to the middle of June 2003). The solid line represents the global mean value and the two dashed lines describe the rms fluctuation of the measurements. This rms variation agrees with the typical uncertainty, so "a'' and "b'' seem to be non-variable sources.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f10.eps} \end{figure}$	Figure 10: $\chi ^2$ spectra for $\alpha = 7$ days (dashed line), $\alpha = 8$ days (solid line), and $\alpha = 9$ days (dotted line). The parameter $\alpha$ is the semiwidth of the bins in the A component, so the three spectra represent different results of a cross-correlation with reasonable time-resolution (the mean sampling time is 6 days/point).
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$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f11.eps} \end{figure}$	Figure 11: $\chi ^2$ spectra for $\alpha = 9$ days (dashed line), $\alpha = 10$ days (solid line), and $\alpha = 11$ days (dotted line), where $\alpha$ is the semiwidth of the bins in the B component.
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$\begin{figure} \par\includegraphics[width=6.5cm,clip]{4283f12.eps} \end{figure}$	Figure 12: Histograms from 1000 repetitions and the $\chi ^2$ minimization (bins in B and $\alpha = 10$ days). Top panel: best solutions of the time delay. Bottom panel: best solutions of the magnitude offset (flux ratio). These distributions are consistent with a delay of about one and a half months and a time-delay-corrected flux ratio of about 0.59 mag.
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$\begin{figure} \par\includegraphics[width=6.8cm,clip]{4283f13.eps} \end{figure}$	Figure 13: Comparison between the shifted A light curve (circles) and the B light curve (squares). We use an $\chi ^2$ minimization, bins in B, and $\alpha = 10$ days. Top panel: best solution ( $\Delta \tau _{\rm BA} = - 44$ days, $\Delta m_{\rm BA} = 0.59$ mag). Bottom panel: solution for $\Delta \tau _{\rm BA} = - 80$ days ( $\Delta m_{\rm BA} = 0.56$ mag).
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$\begin{figure} \par\includegraphics[angle=-90,width=7.5cm,clip]{4283f14.eps} \end{figure}$	Figure 14: Dispersion spectra for $\delta = 7$ days (dashed line), $\delta = 9$ days (solid line), and $\delta = 11$ days (dotted line). The parameter $\delta$ is the decorrelation length associated with the D²_4,2 spectra (Pelt et al. 1996).
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$\begin{figure} \par\includegraphics[width=6.7cm,clip]{4283f15.eps} \end{figure}$	Figure 15: Histograms from 1000 repetitions and the D² minimization ( $\delta = 9$ days). Top panel: best solutions of the time delay. Bottom panel: best solutions of the magnitude offset (flux ratio). These distributions are again consistent with a 1.5-month delay and and a time-delay-corrected flux ratio of about 0.58-0.59 mag.
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