All Figures

$\begin{figure} \par\includegraphics[angle=-90,width=18cm,clip]{F1-mn.eps} \end{figure}$ Figure 1: Optical and UV spectrum of MN Lupi (top spectrum) in comparison with the inactive M0-star HD 209290 (bottom spectrum, shifted by 0.5 in intensity). All hydrogen Balmer lines up to the Balmer jump appear in emission. Strong Ca II H and K, Na D, and He I emission are evident as well as numerous weak telluric features. The very strong forbidden oxygen O I lines are geocoronal in origin. Also notice the lithium absorption line at 670.8 nm.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F2-mn.eps} \end{figure}$ Figure 2: Differential BVRI-photometry of MN Lupi phased with P=0.439 days (only V is shown). Different symbols refer to different nights, i.e. JD 2 452 400+(night number) as following: plusses = +30, asterisks = +31, diamonds = +33, triangles = +34, squares = +35, dots = +36, crosses = +37.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F3-mn.eps} \end{figure}$ Figure 3: Periodogram of MN Lupi from the CLEAN algorithm. The peak at 0.439 days is interpreted to be the rotational period.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F4-mn.eps} \end{figure}$ Figure 4: Heliocentric radial velocities of MN Lupi for both nights. Only absorption lines were used for the cross correlation in order to best represent the photospheric velocities. Note that the error bars are rms values from individual measures of many different wavelength regions relative to the first spectrum and represent best estimates of the true external errors.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F5-mn.eps} \end{figure}$ Figure 5: Evolution of the observed Balmer line profiles. Each panel shows the original spectra in the top, the residuals after subtraction of an average spectrum in the middle, and a grey scale plot of the residuals in the bottom. Time runs from top to bottom with individual spectra offset by an arbitrary constant C. n1refers to the first night, n2 to the second night. Note the dark and bright features that consistently appear throughout the emission profiles. The average equivalent widths are -4.7 Å ( $\pm$ 0.8), -3.9 Å ( $\pm$ 0.9), -3.45 Å ( $\pm$ 0.45), and -4.0 Å ( $\pm$ 0.6) for H $\alpha$ , H $\beta$ , H $\gamma$ , and H $\delta$ , respectively. The number in parentheses is the peak-to-peak variation.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F6-mn.eps} \end{figure}$ Figure 6: Evolution of a) He I and b) Ca II H and H $\epsilon$ . Nomenclature as in Fig. 5.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm]{F7-mn.eps} \end{figure}$ Figure 7: Two examples for the evolution of photospheric absorption line profiles. a) Li I 670.8 nm, b) Fe I 610.2 nm. Nomenclature as in Fig. 5. Note that the Li line appears flat bottomed while the Fe line has a more triangular shape.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.6cm,clip]{F8-mn.eps} \end{figure}$ Figure 8: MN Lupi in the H-R diagram. The dot with error bars is the position of MN Lupi. The full lines are the evolutionary tracks from Baraffe et al. (1998) for masses between 0.4-0.8 solar masses. The dash-dotted lines are the isochrones for 2, 10, 50, and 100 Myr. The comparison suggests a mass for MN Lupi of 0.68 $^{+0.06}_{-0.10}~M_\odot$ and an age of $\approx$ 20 Myr.
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In the text

$\begin{figure} \par\includegraphics[width=15.5cm,clip]{F9-mn.eps} \end{figure}$ Figure 9: Doppler image of MN Lupi for May 27, 2000 (image n1). Maps are plotted in a spherical projection at eight equidistant rotational phases. The temperature scale is indicated and is the same for all projections. The photospheric temperature is 3800 K. A ring of higher temperature around the visible rotational pole suggests remnant heating of the photosphere from accretion shocks. Several hot spots are identified and document the inhomogeneity of the accretion process.
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In the text

$\begin{figure} \par\includegraphics[width=15.5cm,clip]{F10-mn.eps} \end{figure}$ Figure 10: Doppler image of MN Lupi for May 28, 2000 (image n2), separated from image n1 by 14 h or 1.3 stellar rotations. Although the overall surface morphology remained as in image n1, some structures seem to have changed.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=18cm,clip]{F11-mn.eps} \end{figure}$ Figure 11: Observations (crosses) and fits (lines) from the inversion of the Li I 670.8-nm profiles for a) night n1 and b) night n2. Note that the pixels with the cosmic-ray hit in profile n1/313 were given zero weight in the inversion.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8cm,clip]{F12-mn.eps} \end{figure}$ Figure 12: Poloidal field lines and density contours for the inner part of the MN Lupi system (units in stellar radii). The outer boundary is located at r=20. The time unit is the stellar breakup rotation period. The initial disk was computed from a standard model with a viscosity parameter $\alpha =0.01$ , an accretion rate of 10^-11 $M_\odot$ yr^-1 and a Kramers-type opacity law. The (dipole) field strength on the stellar surface is 3 kG at the poles.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F2-mn.eps} \end{figure}$	Figure 2: Differential BVRI-photometry of MN Lupi phased with P=0.439 days (only V is shown). Different symbols refer to different nights, i.e. JD 2 452 400+(night number) as following: plusses = +30, asterisks = +31, diamonds = +33, triangles = +34, squares = +35, dots = +36, crosses = +37.
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$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F3-mn.eps} \end{figure}$	Figure 3: Periodogram of MN Lupi from the CLEAN algorithm. The peak at 0.439 days is interpreted to be the rotational period.
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$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F4-mn.eps} \end{figure}$	Figure 4: Heliocentric radial velocities of MN Lupi for both nights. Only absorption lines were used for the cross correlation in order to best represent the photospheric velocities. Note that the error bars are rms values from individual measures of many different wavelength regions relative to the first spectrum and represent best estimates of the true external errors.
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$\begin{figure} \par\includegraphics[angle=0,width=8.6cm,clip]{F6-mn.eps} \end{figure}$	Figure 6: Evolution of a) He I and b) Ca II H and H $\epsilon$ . Nomenclature as in Fig. 5.
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$\begin{figure} \par\includegraphics[angle=0,width=8.6cm]{F7-mn.eps} \end{figure}$	Figure 7: Two examples for the evolution of photospheric absorption line profiles. a) Li I 670.8 nm, b) Fe I 610.2 nm. Nomenclature as in Fig. 5. Note that the Li line appears flat bottomed while the Fe line has a more triangular shape.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.6cm,clip]{F8-mn.eps} \end{figure}$	Figure 8: MN Lupi in the H-R diagram. The dot with error bars is the position of MN Lupi. The full lines are the evolutionary tracks from Baraffe et al. (1998) for masses between 0.4-0.8 solar masses. The dash-dotted lines are the isochrones for 2, 10, 50, and 100 Myr. The comparison suggests a mass for MN Lupi of 0.68 $^{+0.06}_{-0.10}~M_\odot$ and an age of $\approx$ 20 Myr.
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$\begin{figure} \par\includegraphics[width=15.5cm,clip]{F10-mn.eps} \end{figure}$	Figure 10: Doppler image of MN Lupi for May 28, 2000 (image n2), separated from image n1 by 14 h or 1.3 stellar rotations. Although the overall surface morphology remained as in image n1, some structures seem to have changed.
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$\begin{figure} \par\includegraphics[angle=0,width=18cm,clip]{F11-mn.eps} \end{figure}$	Figure 11: Observations (crosses) and fits (lines) from the inversion of the Li I 670.8-nm profiles for a) night n1 and b) night n2. Note that the pixels with the cosmic-ray hit in profile n1/313 were given zero weight in the inversion.
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