All Figures

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3406fig1.eps} \end{figure}$ Figure 1: Covered orbital separation ranges as function of RV precision and time base of the obtained data for a 0.1 $M_{\odot }$ primary. Top panel: RV semiamplitude vs. orbital separation for different companion masses. With the average RV precision of 190 m s^-1 for primaries of 0.1 $M_{\odot }$ achieved in this survey, a 1 $M_{\rm Jup}$ companion can be detected out to 0.25 AU, a 2 $M_{\rm Jup}$ companion out to 0.9 AU, a 3 $M_{\rm Jup}$ companion out to 2 AU, a 4 $M_{\rm Jup}$ companion out to 3.5 AU, and companions of $\geq$ 5 $M_{\rm Jup}$ at least out to 4 AU. However, due to a limited time base not all of the possible separation ranges have been covered yet. This is displayed in the bottom panel, which shows the orbital period vs separation exemplarily for companion masses of 0.1 $M_{\rm Jup}$ , 20 $M_{\rm Jup}$ , and 60 $M_{\rm Jup}$ . The orbital periods sampled in this survey so far vary among the different targets. For all targets, a period of 40 days has been covered, allowing the detection of substellar companions out to 0.1 AU. For some targets, periods of 150 days, 4 yr, and 8 yr have also been probed and, thus, correspondingly larger separations, as indicated in the plot.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3406fig2.eps} \end{figure}$ Figure 2: Same as Fig. 1 but for a 0.06 $M_{\odot }$ primary for which the RV precision achieved in this survey is 390 m s^-1 on average.
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In the text

$\begin{figure} \par\includegraphics[width=6cm,clip]{3406fig3.eps} \end{figure}$ Figure 3: RV constant objects: relative RV vs. time in Julian days for BDs/VLMSs in Cha I based on high-resolution UVES/VLT spectra. Error bars indicate 1 $\sigma$ errors.
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In the text

$\begin{figure} \par\includegraphics[width=6.2cm,clip]{3406fig4.eps} \end{figure}$ Figure 4: RV constant objects continued. See Fig. 3.
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In the text

$\begin{figure} \par\includegraphics[width=6.2cm,clip]{3406fig5.eps} \end{figure}$ Figure 5: RV constant objects continued. See Fig. 3.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{3406fig6.eps} \end{figure}$ Figure 6: RV constant objects continued. See Fig. 3.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3406fig7.eps} \end{figure}$ Figure 7: RV variations vs. object mass. Plotted are half peak-to-peak differences of the observed RVs. Each data point is labeled with the corresponding object name, the numbers denote the Cha H $\alpha$ objects. The upper three data points represent the RV variable objects with $\Delta$ RV above 1 km s^-1. The remaining data points represent RV constant objects. The decrease of $\Delta$ RV with increasing mass for the latter group indicates that they display no significant RV noise due to activity, which would cause the opposite effect, i.e. an increasing RV amplitude with mass. Mass estimates are from Comerón et al. (1999, 2000). HBML roughly indicates the theoretical "hydrogen burning mass limit''.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3406fig8.eps} \end{figure}$ Figure 8: RV noise level: Same as Fig. 7 but only variations on time scales of days to weeks are considered. Differences to Fig. 7 occur for Cha H $\alpha$ 8 and CHXR 74, whereas for all other objects, either data have been recorded anyway only within one year or the RV variations observed on the short- and long-term do not differ in the recorded amplitude. It can be seen that the downward trend is reversed somewhere between 0.1 and 0.2 $M_{\odot }$ .
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{3406fig9.eps} \end{figure}$ Figure 9: RV variable objects: relative RV vs. time in Julian days for the BD candidate Cha H $\alpha$ 8 and the low-mass stars CHXR 74 and Sz 23 in Cha I based on UVES/VLT spectra. Error bars indicate 1 $\sigma$ errors.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3406fig2.eps} \end{figure}$	Figure 2: Same as Fig. 1 but for a 0.06 $M_{\odot }$ primary for which the RV precision achieved in this survey is 390 m s^-1 on average.
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$\begin{figure} \par\includegraphics[width=6cm,clip]{3406fig3.eps} \end{figure}$	Figure 3: RV constant objects: relative RV vs. time in Julian days for BDs/VLMSs in Cha I based on high-resolution UVES/VLT spectra. Error bars indicate 1 $\sigma$ errors.
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$\begin{figure} \par\includegraphics[width=6.2cm,clip]{3406fig4.eps} \end{figure}$	Figure 4: RV constant objects continued. See Fig. 3.
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$\begin{figure} \par\includegraphics[width=6.2cm,clip]{3406fig5.eps} \end{figure}$	Figure 5: RV constant objects continued. See Fig. 3.
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$\begin{figure} \par\includegraphics[width=14cm,clip]{3406fig6.eps} \end{figure}$	Figure 6: RV constant objects continued. See Fig. 3.
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$\begin{figure} \par\includegraphics[width=14cm,clip]{3406fig9.eps} \end{figure}$	Figure 9: RV variable objects: relative RV vs. time in Julian days for the BD candidate Cha H $\alpha$ 8 and the low-mass stars CHXR 74 and Sz 23 in Cha I based on UVES/VLT spectra. Error bars indicate 1 $\sigma$ errors.
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