All Figures

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{0446fig1.eps}\end{figure}$ Figure 1: B, V, R, and I band light curves during the 2001 observations. Time is measured in hours from 19:00 UT on March 26, 2001. The small filled diamonds below the B band light curve of 4 show the B band light curve of the comparison star 2 (open diamonds in the left panel show the R band light curve of the same star). For clarity reasons, the standard star light curves are shifted to the same level of $\sim$ 0.35 mJy.
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In the text

$\begin{figure} \par\includegraphics[height=7.65cm,width=8.6cm,clip]{0446fig2.eps}\end{figure}$ Figure 2: B and I band light curves during the 2002 observations. Time is measured in hours from 18:00 UT on May 23, 2002. As before with Fig. 1, the small filled diamonds show the B band light curve of the comparison star 2 (shifted to a mean of $\sim$ 0.033 mJy).
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In the text

$\begin{figure} \par\includegraphics[height=7.65cm,width=8.45cm,clip]{0446fig3.eps}\end{figure}$ Figure 3: B and I band light curves in 2002 (filled squares and open circles, respectively) normalized to their average flux level. Time is measured in hours from the beginning (plus half an hour) of the May 28 B band observations. In order to reduce the experimental noise, we have smoothed the May 28, 29 and 30 light curves using a bin size of 3, 6, and 4, respectively.
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In the text

$\begin{figure} \par\includegraphics[height=7.65cm,width=8.3cm,clip]{0446fig4.eps}\end{figure}$ Figure 4: Same as Fig. 3 for the April, 2001 light curves (filled squares, filled circles, open squares, and open circles show the B, V, R, and I band light curves, respectively). The light curves have been smoothed out using a bin size of 3, except from the last point where a bin size of 2 was used. Time is measured in hours from the start of the April 18, B band observations.
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In the text

$\begin{figure} \par\includegraphics[height=7.75cm,width=8.3cm,clip]{0446fig5.eps}\end{figure}$ Figure 5: B-I spectral index vs. the B+I normalized flux for the 2002 observations. For clarity reasons, we have smoothed the data using the same bin size that we have used for the respective light curves in Fig. 3. The dotted lines show the best linear model fit to the data, while the arrows indicate the flux variability trend (i.e. flux increase or decrease) during the observations (see text for details).
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In the text

$\begin{figure} \par\includegraphics[height=7.75cm,width=8.35cm,clip]{0446fig6.eps}\end{figure}$ Figure 6: B-I (filled black circles and crosses) and V-I (grey filled circles and crosses) spectral indices vs the B+I and V+Inormalized source flux for the 2001 observations. The data have been smoothed out using the same bin size as with the respective light curves in Fig. 4.
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In the text

$\begin{figure} \par\includegraphics[height=7.75cm,width=8.3cm,clip]{0446fig7.eps}\end{figure}$ Figure 7: The Discrete Correlation Function between the B and I band light curves during the late May 2002 observations. Significant correlation at positive lags means that the B band variations are leading the I band. The solid line shows the best fitting Gaussian model to the data.
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In the text

$\begin{figure} \par\includegraphics[height=7.65cm,width=8.6cm,clip]{0446fig2.eps}\end{figure}$	Figure 2: B and I band light curves during the 2002 observations. Time is measured in hours from 18:00 UT on May 23, 2002. As before with Fig. 1, the small filled diamonds show the B band light curve of the comparison star 2 (shifted to a mean of $\sim$ 0.033 mJy).
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$\begin{figure} \par\includegraphics[height=7.65cm,width=8.45cm,clip]{0446fig3.eps}\end{figure}$	Figure 3: B and I band light curves in 2002 (filled squares and open circles, respectively) normalized to their average flux level. Time is measured in hours from the beginning (plus half an hour) of the May 28 B band observations. In order to reduce the experimental noise, we have smoothed the May 28, 29 and 30 light curves using a bin size of 3, 6, and 4, respectively.
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$\begin{figure} \par\includegraphics[height=7.65cm,width=8.3cm,clip]{0446fig4.eps}\end{figure}$	Figure 4: Same as Fig. 3 for the April, 2001 light curves (filled squares, filled circles, open squares, and open circles show the B, V, R, and I band light curves, respectively). The light curves have been smoothed out using a bin size of 3, except from the last point where a bin size of 2 was used. Time is measured in hours from the start of the April 18, B band observations.
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$\begin{figure} \par\includegraphics[height=7.75cm,width=8.35cm,clip]{0446fig6.eps}\end{figure}$	Figure 6: B-I (filled black circles and crosses) and V-I (grey filled circles and crosses) spectral indices vs the B+I and V+Inormalized source flux for the 2001 observations. The data have been smoothed out using the same bin size as with the respective light curves in Fig. 4.
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$\begin{figure} \par\includegraphics[height=7.75cm,width=8.3cm,clip]{0446fig7.eps}\end{figure}$	Figure 7: The Discrete Correlation Function between the B and I band light curves during the late May 2002 observations. Significant correlation at positive lags means that the B band variations are leading the I band. The solid line shows the best fitting Gaussian model to the data.
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