All Figures

$\begin{figure} \par\includegraphics[angle=-90,width=15cm,clip]{3951fig1.ps}\end{figure}$ Figure 1: Blue/green spectrum of BD $+53\hbox {$^\circ $ }$ 2790, taken on July 21, 2000 with the 1.3-m telescope at Skinakas. Only the strongest features have been indicated. For a more complete listing of photospheric features visible in the spectrum, see NR01. The spectrum has been normalised by dividing a spline fit into the continuum. A normalised spectrum of 10 Lac (09V), shifted down for plotting purposes, is also shown for comparison.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=11cm,clip]{3951fig2.ps} \end{figure}$ Figure 2: Evolution of the H $\alpha$ line profile of BD $+53^{\circ }$ 2790 during 1986-2000. All spectra have had the continuum level normalised and are offset vertically to allow direct comparison.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=6cm,clip]{3951fig3.ps}\end{figure}$ Figure 3: Parameters of the H $\alpha$ emission line for all the red spectra from the INT.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.6cm,clip]{3951fig4.ps}\end{figure}$ Figure 4: EW of the He I $\lambda$ 6678 Å line versus that of the H $\alpha$ line. There seems to be some degree of correlation between both quantities. Only data from INT spectra where both lines were visible are shown. A linear regresion fit to the data is shown as a dashed line. The correlation coefficient of the regression is r=0.62 and the correlation is significant at a 98% confidence level.
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In the text

$\begin{figure} \par\includegraphics[width=10.6cm,clip]{3951fig5.ps}\end{figure}$ Figure 5: The spectrum of BD + $53^{\circ }$ 2790 in the yellow/red/near-IR. Echelle spectrum taken on 17th August 1999 using the 1.52-m G. D. Cassini Telescope equipped with BFOSC and grisms #9 (echelle) and #13 (cross-disperser). All the orders have been flattened by division into a spline fit to the continuum.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3951fig6.ps}\end{figure}$ Figure 6: K-band spectra of BD $+53\hbox {$^\circ $ }$ 2790. The top spectrum was taken on July 7, 1994, and the bottom one on July 8, 1994.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{3951fig7.ps}\end{figure}$ Figure 7: Infrared light curves of BD $+53\hbox {$^\circ $ }$ 2790, taken during 1987-2001.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=12.5cm,clip]{3951fig8.ps}\end{figure}$ Figure 8: Colour-magnitude plots showing the evolution of the infrared magnitudes. The strong correlation seen in the K/(H-K) plane is not a simple reflection of the fact that a brighter K means a smaller (H-K), as the correlation between H and K is also strong. Regression lines are shown as dashed lines. In the first case the correlation coefficient is r_(H-K),K=-0.46 and the correlation is significant in a 98% confidence level. In the latter case the correlatino coefficient is r_H,K=0.80 and the correlation is also significant at a 98% confidence level.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{3951fig9.ps}\end{figure}$ Figure 9: Evolution of the infrared colours in BD $+53\hbox {$^\circ $ }$ 2790 during 1987-1999 compared to that of the EW of H $\alpha$ . Since simultaneous measurements are rare, we cannot properly search for correlations. The lack of any obvious correlated trends could be caused by the lack of long-term trends.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{3951fig10.ps}\end{figure}$ Figure 10: H $\alpha$ parameters - EW (in Å), FWHM (in Å), peak separation (in km s^-1) and V/R ratio- for the monitoring campaign in July 2000. There seems to be a high degree of correlation in the evolution of EW, FWHM and peak separation, which is not shared by the V/R ratio.
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In the text

$\begin{figure} \par\includegraphics[width=6cm,clip]{3951fig11.eps}\end{figure}$ Figure 11: Evolution of H $\alpha$ line in BD $+53\hbox {$^\circ $ }$ 2790 during the monitoring campaign in July 2000. Note the moderate night-to-night changes of the line profile and the important difference between the spectra from the first and second week.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{3951fig12.eps}\end{figure}$ Figure 12: Normalised profiles of selected He I lines (namely, He I $\lambda$ 4026, $\lambda$ 4144, $\lambda$ 4388, and $\lambda$ 4471 Å) from BD $+53\hbox {$^\circ $ }$ 2790 together with those of the same lines from 10 Lac but artificially broadened to 200 km s^-1 and to those rotational velocities yielding upper and lower envelopes to the with of the BD $+53\hbox {$^\circ $ }$ 2790 lines (their values are shown at the peak of the profile, in units of km s^-1). In all cases rotational velocities above 200 km s^-1 are needed to reproduce the line widths.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=11cm,clip]{3951fig2.ps} \end{figure}$	Figure 2: Evolution of the H $\alpha$ line profile of BD $+53^{\circ }$ 2790 during 1986-2000. All spectra have had the continuum level normalised and are offset vertically to allow direct comparison.
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$\begin{figure} \par\includegraphics[angle=-90,width=6cm,clip]{3951fig3.ps}\end{figure}$	Figure 3: Parameters of the H $\alpha$ emission line for all the red spectra from the INT.
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$\begin{figure} \par\includegraphics[width=10.6cm,clip]{3951fig5.ps}\end{figure}$	Figure 5: The spectrum of BD + $53^{\circ }$ 2790 in the yellow/red/near-IR. Echelle spectrum taken on 17th August 1999 using the 1.52-m G. D. Cassini Telescope equipped with BFOSC and grisms #9 (echelle) and #13 (cross-disperser). All the orders have been flattened by division into a spline fit to the continuum.
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$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3951fig6.ps}\end{figure}$	Figure 6: K-band spectra of BD $+53\hbox {$^\circ $ }$ 2790. The top spectrum was taken on July 7, 1994, and the bottom one on July 8, 1994.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{3951fig7.ps}\end{figure}$	Figure 7: Infrared light curves of BD $+53\hbox {$^\circ $ }$ 2790, taken during 1987-2001.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{3951fig9.ps}\end{figure}$	Figure 9: Evolution of the infrared colours in BD $+53\hbox {$^\circ $ }$ 2790 during 1987-1999 compared to that of the EW of H $\alpha$ . Since simultaneous measurements are rare, we cannot properly search for correlations. The lack of any obvious correlated trends could be caused by the lack of long-term trends.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.4cm,clip]{3951fig10.ps}\end{figure}$	Figure 10: H $\alpha$ parameters - EW (in Å), FWHM (in Å), peak separation (in km s^-1) and V/R ratio- for the monitoring campaign in July 2000. There seems to be a high degree of correlation in the evolution of EW, FWHM and peak separation, which is not shared by the V/R ratio.
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$\begin{figure} \par\includegraphics[width=6cm,clip]{3951fig11.eps}\end{figure}$	Figure 11: Evolution of H $\alpha$ line in BD $+53\hbox {$^\circ $ }$ 2790 during the monitoring campaign in July 2000. Note the moderate night-to-night changes of the line profile and the important difference between the spectra from the first and second week.
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