All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{3535_f1.ps} \end{figure}$ Figure 1: Composite EPIC (MOS1+MOS2+PN) image of the Praesepe field.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{3535_f2.ps} \end{figure}$ Figure 2: EPIC MOS1+MOS2+PN background-subtracted light curve of the M-type Praesepe candidate 2MASS J0839531+192403. Data are binned over 600 s.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{3535_f3.ps} \end{figure}$ Figure 3: 2MASS H-band image of WRS 4 and GSC2 N231230081115, with superimposed the contour levels of the blended X-ray source. X-ray contours correspond to 0.24, 0.32, 0.40, 0.48, 0.56, 0.64 cts/arcsec².
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{3535_f4.ps}\end{figure}$ Figure 4: Comparison of the X-ray luminosities of Praesepe members falling in the XMM- Newton field of view derived from XMM- Newton and ROSAT. Different symbols are used for A stars (open triangles), early F stars (filled triangles), late F-G stars (filled circles), K stars (diamonds), M stars (squares) and giants (asterisks). $1\sigma$ errors are shown for X-ray detections, while upper limits are indicated by an arrow (where error bars are not shown, they are smaller than the symbol size). Dotted lines indicate variations of a factor of two in the X-ray luminosity. Stars that have changed by more than this factor are labeled with their corresponding KW numbers (Klein-Wassink 1927).
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=17.5cm,clip]{3535_f5.ps}\end{figure}$ Figure 5: Comparison of the XLDF of Praesepe (solid line) and the Hyades (dash-dotted line) for late F-G dwarf stars in the colour range $0.50 \le B-V \le 0.81$ . In panel a) we show the Praesepe XLDF obtained from the present XMM- Newton data. Panel b) shows the XLDF derived, for the same sample of stars, from the previous ROSAT observations; for comparison, we also show the Praesepe XLDF derived from the entire ROSAT sample (dotted line). The Hyades XLDF was derived from the ROSAT observations by Stern et al. (1995).
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In the text

$\begin{figure} \par {\includegraphics[angle=-90,width=8.5cm,clip]{3535_f6.ps} }\end{figure}$ Figure 6: $\log n$ (Li) vs. $T_{\rm eff}$ for Praesepe members with available X-ray data. Lithium data have been retrieved from Soderblom et al. (1993). Filled symbols denote stars with $\log L_{\rm X} \leq 28.6$ erg s^-1, while crossed symbols indicate photometric and/or spectroscopic binaries.
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In the text

$\begin{figure} \par {\includegraphics[angle=90,width=17.5cm,clip]{3535_f7.ps} } \end{figure}$ Figure 7: Comparison of the XLDF of Praesepe (solid line) and the Hyades (dash-dotted line) for K dwarfs ( $0.82 \le B-V \le 1.40$ , left panel) and M dwarfs ( $B-V \ge 1.41$ , right panel). The Hyades XLDF was derived from the ROSAT observations by Stern et al. (1995) and Pye et al. (1994).
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In the text

$\begin{figure} \par {\includegraphics[width=8.5cm,clip]{3535_f8.ps} }\end{figure}$ Figure 8: PN spectra of the three brightest sources in the Praesepe field. The best-fit model is also shown. For KW 212 and KW 181 the emission is dominated by background above 2 keV.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{3535_f1.ps} \end{figure}$	Figure 1: Composite EPIC (MOS1+MOS2+PN) image of the Praesepe field.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{3535_f2.ps} \end{figure}$	Figure 2: EPIC MOS1+MOS2+PN background-subtracted light curve of the M-type Praesepe candidate 2MASS J0839531+192403. Data are binned over 600 s.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{3535_f3.ps} \end{figure}$	Figure 3: 2MASS H-band image of WRS 4 and GSC2 N231230081115, with superimposed the contour levels of the blended X-ray source. X-ray contours correspond to 0.24, 0.32, 0.40, 0.48, 0.56, 0.64 cts/arcsec².
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$\begin{figure} \par {\includegraphics[angle=-90,width=8.5cm,clip]{3535_f6.ps} }\end{figure}$	Figure 6: $\log n$ (Li) vs. $T_{\rm eff}$ for Praesepe members with available X-ray data. Lithium data have been retrieved from Soderblom et al. (1993). Filled symbols denote stars with $\log L_{\rm X} \leq 28.6$ erg s^-1, while crossed symbols indicate photometric and/or spectroscopic binaries.
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$\begin{figure} \par {\includegraphics[angle=90,width=17.5cm,clip]{3535_f7.ps} } \end{figure}$	Figure 7: Comparison of the XLDF of Praesepe (solid line) and the Hyades (dash-dotted line) for K dwarfs ( $0.82 \le B-V \le 1.40$ , left panel) and M dwarfs ( $B-V \ge 1.41$ , right panel). The Hyades XLDF was derived from the ROSAT observations by Stern et al. (1995) and Pye et al. (1994).
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$\begin{figure} \par {\includegraphics[width=8.5cm,clip]{3535_f8.ps} }\end{figure}$	Figure 8: PN spectra of the three brightest sources in the Praesepe field. The best-fit model is also shown. For KW 212 and KW 181 the emission is dominated by background above 2 keV.
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