All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2995fig1.eps} \end{figure}$ Figure 1: The dependence on brightness of the rms deviation of stellar magnitudes of the variable and the comparison stars on the corresponding sample mean values. Open circles - for the night 53 035 with relatively good weather, open triangles - for the night 53 026 with highly variable atmospheric transparency. The curved lines correspond to the best fit assuming the Poisson noise for the counts of the star and background. Horizontal lines correspond to the estimated accuracy of the "artificial'' mean weighted comparison star. The bottom curve in these two pairs correspond to better atmospheric conditions and thus smaller error estimates. Please note that the brightness is calibrated using results from the night 53 035, thus the points for the night 53 036 with worse weather are shifted towards larger apparent magnitude and larger error estimates. Vertical lines project mean magnitude of BG CMi onto corresponding "accuracy-brightness'' dependence.
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In the text

$\begin{figure} \par\includegraphics[width=17cm,clip]{2995fig2.eps} \end{figure}$ Figure 2: The brightness variations of BG CMi during our observations with orbital phase computed using the ephemeris (4) by Patterson & Thomas (1993). Left: original data; right: "running sine'' fit $X_{\rm RS}(t,t,\Delta t)$ for times of observations and corresponding local mean $a(t,t,\Delta t).$ In the fits, some points have been skipped because of large error estimates of the smoothing value (> $0\hbox{$.\!\!^{\rm m}$ }10)$ near the gaps of the observations.
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{2995fig3.eps} \end{figure}$ Figure 3: The multi-sinusoidal fit for individual runs of observations of BG CMi. The orbital light curve is shown as an abridged sum (s=6), whereas the "orbital+spin'' variations are fitted by a complete sum (s=7). The fits have been computed for fluxes, following de Martino et al. (1995), and converted to stellar magnitudes for comparison with the original data and the "running sine'' fits. For R, the magnitude is expressed as the "Var-Comp'' difference.
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{2995fig4.eps} \end{figure}$ Figure 4: Brightness and color variations for original and interpolated points (dots) and approximations of the orbital and "orbital+spin'' variability.
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{2995fig5.eps} \end{figure}$ Figure 5: Two-color diagram for the deviations of original and interpolated points from orbital fit (dots). The line corresponds to the unitary slope $\Delta R=\Delta V.$ The closed lines correspond to the orbital fit (shifted by $+0\hbox{$.\!\!^{\rm m}$ }1$ in V and $-0\hbox{$.\!\!^{\rm m}$ }1$ in R) and deviations of the "spin+orbital'' fit from the pure "orbital'' one. The orbital curve is shifted by $+0\hbox{$.\!\!^{\rm m}$ }1,-0\hbox{$.\!\!^{\rm m}$ }1$ for illustrating purposes. The cross indicates $\pm$ $1\sigma$ values for accuracy of the smoothed curves in V and R.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{2995fig6.eps} \end{figure}$ Figure 6: Periodograms S(f) for deviations of the brightness and color from the orbital fits for two nights of two-color photometry. Vertical lines mark positions of the orbital $(\Omega )$ frequency and its harmonics, as well as of the spin $(\omega )$ frequency and its harmonic $(2\omega )$ and sidebands $(\omega \pm \Omega )$ . Numbers correspond to the frequencies suspected by Hellier (1999) and Paterson & Thomas (1993).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2995fig7.eps} \end{figure}$ Figure 7: The dependence of the test function $\Lambda (\Delta t)$ on the filter half-width $\Delta t.$ The two highest peaks correspond to the spin and theharmonic of the orbital variability.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2995fig8.eps} \end{figure}$ Figure 8: The dependence on the orbital phase of the local mean and semi-amplitude of the spin variability.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2995fig9.eps} \end{figure}$ Figure 9: O-C values for times of spin maxima calculated with the linear ephemeris (Pych et al. 1996) with a cycle numbering corresponding to the best 4th order polynomial fit. Fits are shown, which correspond to ephemerides published by Patterson & Thomas (1993), Garlick et al. (1994) and Pych et al. (1996) for polynomials of order 2, 3 and 2, respectively. The order of our polynomial fits with optimal cycle counting are marked by numbers. Our parabolic fit is close to that of Pych et al. (1996) and is not shown separately. Because of possible cycle miscount after the gap, our data are shown with shifts of integer number of periods.
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{2995fig4.eps} \end{figure}$	Figure 4: Brightness and color variations for original and interpolated points (dots) and approximations of the orbital and "orbital+spin'' variability.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2995fig7.eps} \end{figure}$	Figure 7: The dependence of the test function $\Lambda (\Delta t)$ on the filter half-width $\Delta t.$ The two highest peaks correspond to the spin and theharmonic of the orbital variability.
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2995fig8.eps} \end{figure}$	Figure 8: The dependence on the orbital phase of the local mean and semi-amplitude of the spin variability.
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