All Figures

$\begin{figure} \par {\includegraphics[width=11.8cm,clip]{fig1.ps} } \end{figure}$ Figure 1: Merged image of EPIC pn, MOS 1 and MOS 2 for the center of the Cha I South cloud. The positions of all 58 detected sources are marked by circles (radius = $10^{\prime \prime }$ ). Numbers refer to the designations in Col. 1 of Table 2.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.8cm,clip]{fig2.eps} } \end{figure}$ Figure 2: J-H / H-K diagram showing the position of the eight X-ray detected Cha I candidates without spectroscopic information. The sources with 2 MASS counterparts are labeled with their X-ray source number, objects known before this study are referenced by their previous designation. We use published NIR photometry for KG 2001-5 (Kenyon & Gómez2001) and 2 MASS data for all other objects. The solid and the dotted curves are the loci of dwarf and giant stars according to Bessell88.1. The dashed lines indicate a reddening corresponding to $A_{\rm V}=10$ mag using the extinction law by RL85.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{fig3a.eps}\vspace*{2mm} \includegraphics[width=8.4cm,clip]{fig3b.eps}\end{figure}$ Figure 3: HRD for counterparts to X-ray sources in the XMM-Newton field. Tracks and isochrones that span the full range required to obtain masses and ages for the Cha I sample are from Baraffe98.1 ( top) and Palla99.1 ( bottom). Counterparts of X-ray sources which have not been spectroscopically studied are shown as circles, and spectroscopic cloud members as x-points. The distance assumed is 160 pc.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.8cm]{fig4.eps} } \end{figure}$ Figure 4: EPIC pn spectrum of CHX 10a overlaid by the 1-T (dotted histogram) and 2-T (solid histogram) bestfit model. The lower panel shows the $\chi ^2$ residuals. Clearly the 1-T model does not adequately describe the data.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{fig5a.eps}\vspace*{3mm} \includegraphics[width=8.8cm,clip]{fig5b.eps}\end{figure}$ Figure 5: Hardness ratio diagrams for known Cha I members in the XMM-Newton field. ${\it HR}~1$ compares the hard 1 (1.0-2.4 keV) and the soft (0.3-1.0 keV) band, and ${\it HR}~2$ compares the hard 2 (2.4-7.8 keV) and the hard 1 band. Also shown is a grid of column density and temperature corresponding to the hardness ratios derived from the count rates of a 1-T thermal Raymond-Smith model within PIMMS taking account of the different spectral response of pn ( top panel) and MOS ( bottom panel). Hardness ratios for each source are derived from the number of source counts in the respective energy bands: filled circles - bright Cha I members (spectral sample), open circles - faint Cha I members.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.6cm,clip]{fig6.eps} } \end{figure}$ Figure 6: Comparison of the X-ray luminosities of X-ray bright Cha I objects derived with two different approaches: x-axis - using the ${\it HR}$ to guess the spectral model which is converted to X-ray flux using PIMMS, and y-axis - from the X-ray spectrum using XSPEC. Filled plotting symbols denote stars which cannot be described by a 1-T model. As can be seen, for these stars the ${\it HR}$ tend to provide a wrong estimate of $L_{\rm x}$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.55cm,clip]{fig7a.eps}\vspace*{2mm} \includegraphics[width=8.4cm,clip]{fig7b.eps}\end{figure}$ Figure 7: Broad-band EPIC lightcurve of the cTTS BYB 43 and the wTTS CHXR-25 displaying flares. The dotted line represents the background extracted from an adjacent source-free region. The background has been scaled to the size of the extraction area for the source photons.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.5cm,clip]{fig8.eps} } \end{figure}$ Figure 8: Broad-band MOS 2 lightcurve of CCE 98-32. The lower curve is the background lightcurve, with count rate scaled corresponding to the extraction area.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.8cm,clip]{fig9.ps} } \end{figure}$ Figure 9: Merged image of EPIC pn, MOS 1 and MOS 2 showing all VLM H ${\alpha }$ emitters in Cha I from the survey by CNK00. The IR positions of Cha H ${\alpha }$ 1...13 are indicated by squares and numbers. Small circles are XMM-Newton sources, and large circles represent the ROSAT PSPC error boxes of $25^{\prime \prime }$ radius at the IR position of those ChaH ${\alpha }$ objects detected with ROSAT; no ROSAT X-ray positions are given in the literature.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{fig10a.eps}\vspace*{2mm} \... ...10b.eps}\vspace*{2mm} \includegraphics[width=8.6cm,clip]{fig10c.eps}\end{figure}$ Figure 10: Broad-band X-ray lightcurves of three VLM objects in Cha I: ChaH ${\alpha }$ 13 and ChaH ${\alpha }$ 8 barely emerge from the background outside flares, while ChaH ${\alpha }$ 3 is clearly visible throughout the observing time.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{fig11a.eps}\vspace*{5mm} \includegraphics[width=8.7cm,clip]{fig11b.eps}\end{figure}$ Figure 11: EPIC pn and MOS hardness ratios for unidentified X-ray sources overplotted on a grid of column density and temperature for a 1-T thermal model; see Fig. 5 and text in Sect. 4.1 for more details. Most objects are harder than typical spectra for the bulk of Cha I stars, suggesting either very young and strongly absorbed cloud members or extragalactic origin (see text in Sect. 6.6).
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.4cm,clip]{fig12.eps} } \end{figure}$ Figure 12: Relative X-ray brightness of stars in Cha I during the XMM-Newton and the ROSAT observation. Count rates refer to the 0.4-2.5 keV band. Only stars detected by both satellites are shown. The dotted lines embrace variations by a factor two and less.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.05cm,clip]{fig13.eps} } \end{figure}$ Figure 13: X-ray versus bolometric luminosity. Different plotting symbols denote different methods to derive $L_{\rm x}$ : filled circles - spectral fits with 2-T models and column density derived from A_J; open squares - assumed 1-T model with $\log{T} = 6.95$ and A_J from the literature; open triangles - assumed 1-T model with $\log{T} = 6.95$ and A_J derived from the JHK color-color diagram (Fig. 2).
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=8.7cm,clip]{fig14.eps} } \end{figure}$ Figure 14: Ratio of X-ray to bolometric luminosity versus mass derived from the PMS models by Baraffe98.1 and Palla99.1. The meaning of the plotting symbols is the same as in Fig. 13. Note the large spread for intermediate-mass which likely reflects directly the changes in the interior structure.
Open with DEXTER

In the text

$\begin{figure} \par {\includegraphics[width=11.8cm,clip]{fig1.ps} } \end{figure}$	Figure 1: Merged image of EPIC pn, MOS 1 and MOS 2 for the center of the Cha I South cloud. The positions of all 58 detected sources are marked by circles (radius = $10^{\prime \prime }$ ). Numbers refer to the designations in Col. 1 of Table 2.
Open with DEXTER

$\begin{figure} \par {\includegraphics[width=8.8cm]{fig4.eps} } \end{figure}$	Figure 4: EPIC pn spectrum of CHX 10a overlaid by the 1-T (dotted histogram) and 2-T (solid histogram) bestfit model. The lower panel shows the $\chi ^2$ residuals. Clearly the 1-T model does not adequately describe the data.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.55cm,clip]{fig7a.eps}\vspace*{2mm} \includegraphics[width=8.4cm,clip]{fig7b.eps}\end{figure}$	Figure 7: Broad-band EPIC lightcurve of the cTTS BYB 43 and the wTTS CHXR-25 displaying flares. The dotted line represents the background extracted from an adjacent source-free region. The background has been scaled to the size of the extraction area for the source photons.
Open with DEXTER

$\begin{figure} \par {\includegraphics[width=8.5cm,clip]{fig8.eps} } \end{figure}$	Figure 8: Broad-band MOS 2 lightcurve of CCE 98-32. The lower curve is the background lightcurve, with count rate scaled corresponding to the extraction area.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{fig10a.eps}\vspace{2mm} \... ...10b.eps}\vspace{2mm} \includegraphics[width=8.6cm,clip]{fig10c.eps}\end{figure}$	Figure 10: Broad-band X-ray lightcurves of three VLM objects in Cha I: ChaH ${\alpha }$ 13 and ChaH ${\alpha }$ 8 barely emerge from the background outside flares, while ChaH ${\alpha }$ 3 is clearly visible throughout the observing time.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{fig11a.eps}\vspace*{5mm} \includegraphics[width=8.7cm,clip]{fig11b.eps}\end{figure}$	Figure 11: EPIC pn and MOS hardness ratios for unidentified X-ray sources overplotted on a grid of column density and temperature for a 1-T thermal model; see Fig. 5 and text in Sect. 4.1 for more details. Most objects are harder than typical spectra for the bulk of Cha I stars, suggesting either very young and strongly absorbed cloud members or extragalactic origin (see text in Sect. 6.6).
Open with DEXTER

$\begin{figure} \par {\includegraphics[width=8.4cm,clip]{fig12.eps} } \end{figure}$	Figure 12: Relative X-ray brightness of stars in Cha I during the XMM-Newton and the ROSAT observation. Count rates refer to the 0.4-2.5 keV band. Only stars detected by both satellites are shown. The dotted lines embrace variations by a factor two and less.
Open with DEXTER

$\begin{figure} \par {\includegraphics[width=8.7cm,clip]{fig14.eps} } \end{figure}$	Figure 14: Ratio of X-ray to bolometric luminosity versus mass derived from the PMS models by Baraffe98.1 and Palla99.1. The meaning of the plotting symbols is the same as in Fig. 13. Note the large spread for intermediate-mass which likely reflects directly the changes in the interior structure.
Open with DEXTER