Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0439fig1.eps} \end{figure}$ Figure 1: Composite R-band flux light curve ( top, mJy) and radio light curves (Jy) at 37 and 22 GHz from the Metsähovi Radio Observatory and at 14.5, 8.0, and 4.8 GHz from UMRAO; red (grey) optical dots represent literature data, while blue (dark) ones show data taken by the WEBT collaboration; grey horizontal and vertical lines have been drawn to guide the eye through the flux variations; the yellow (shaded) area highlights the period considered by Villata et al. (2004); the number of data is indicated in each panel: in the case of optical data, the R-converted B data have been distinguished from the "true" R-band fluxes inside the yellow (shaded) region.
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In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{0439fig2.eps} \end{figure}$ Figure 2: Power spectrum of the discrete Fourier transform ( top panel), autocorrelation function ( middle panel), and structure function changed in sign ( bottom panel) obtained from the 4.8 GHz data; in the top panel the blue dotted line marks the level above which the significance is better than 0.001; dashed vertical lines indicate peak/centroid values of the major peaks. In the middle panel the mean ACF obtained after 1000 FR/RSS Monte Carlo realizations is shown (red dotted line), as well as the percentage of occurrence of the centroid values in the same realizations (insets).
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In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{0439fig3.eps} \end{figure}$ Figure 3: Power spectrum of the discrete Fourier transform ( top panel), autocorrelation function ( middle panel), and structure function changed in sign ( bottom panel) obtained from the 8.0 GHz data; in the top panel the blue dotted line marks the level above which the significance is better than 0.001; dashed vertical lines in the first two panels indicate peak/centroid values of the major peaks. In the middle panel the percentage of occurrence of the ACF centroid values after 1000 FR/RSS Monte Carlo realizations is shown (insets). Coloured strips in the bottom panel indicate the centroid ranges obtained by the FR/RSS Monte Carlo simulations of the ACF, and the coloured line reports the position of the DFT peak.
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In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{0439fig4.eps} \end{figure}$ Figure 4: Power spectrum of the discrete Fourier transform ( top panel), autocorrelation function ( middle panel), and structure function changed in sign ( bottom panel) obtained from the 14.5 GHz data; in the top panel the blue dotted line marks the level above which the significance is better than 0.001; dashed vertical lines in the first two panels indicate peak/centroid values of the major peaks. In the middle panel the percentage of occurrence of the ACF centroid values after 1000 FR/RSS Monte Carlo realizations is shown (insets). Coloured strips in the bottom panel indicate the centroid ranges obtained by the FR/RSS Monte Carlo simulations of the ACF, and the coloured line reports the position of the DFT peak.
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In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{0439fig5.eps} \end{figure}$ Figure 5: Power spectrum of the discrete Fourier transform ( top panel), autocorrelation function ( middle panel), and structure function changed in sign ( bottom panel) obtained from the optical magnitudes; in the top panel the red dotted curve displays the power spectrum obtained from the optical fluxes, and the blue dotted line marks the level above which the significance is better than 0.001.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0439fig6.eps}\end{figure}$ Figure 6: Discrete correlation function between 22 and 14.5 GHz data (red/grey), 22 and 8.0 GHz data (green/light grey), and 22 and 4.8 GHz data (blue/dark); vertical dotted lines indicate the distribution centroids.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0439fig7.eps}\end{figure}$ Figure 7: Discrete correlation function between 14.5 and 8.0 GHz data (red/grey), 8.0 and 4.8 GHz data (green/light grey), and 14.5 and 4.8 GHz data (blue/dark); vertical dotted lines indicate the distribution centroids.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0439fig8.eps} \end{figure}$ Figure 8: R-band flux light curve ( top, mJy) and radio light curves (Jy) at 22, 14.5, and 4.8 GHz with their smoothing cubic splines underplotted; grey horizontal and vertical lines have been drawn to guide the eye through the flux variations; the fifth and sixth panels show the 22 (blue/dark) and 14.5 GHz (green/light grey) splines, respectively, both compared with the 4.8 GHz one (red/grey); the regions where the higher-frequency spline exceeds the lower-energy one have been highlighted; in the top panel the corresponding hardness ratios have been plotted (after shifting, see text for details) for comparison with the optical fluxes.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0439fig9.eps}\end{figure}$ Figure 9: Discrete correlation function between the optical fluxes and the hardness ratio H₂₂ (see text); a fair correlation is found at a time lag of $\sim$ 100 days.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0439fig6.eps}\end{figure}$	Figure 6: Discrete correlation function between 22 and 14.5 GHz data (red/grey), 22 and 8.0 GHz data (green/light grey), and 22 and 4.8 GHz data (blue/dark); vertical dotted lines indicate the distribution centroids.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0439fig7.eps}\end{figure}$	Figure 7: Discrete correlation function between 14.5 and 8.0 GHz data (red/grey), 8.0 and 4.8 GHz data (green/light grey), and 14.5 and 4.8 GHz data (blue/dark); vertical dotted lines indicate the distribution centroids.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0439fig9.eps}\end{figure}$	Figure 9: Discrete correlation function between the optical fluxes and the hardness ratio H₂₂ (see text); a fair correlation is found at a time lag of $\sim$ 100 days.
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