All Figures

$\begin{figure} \par\resizebox{6.5cm}{!}{\includegraphics[clip]{1009fig1.eps}}\end{figure}$ Figure 1: H band images of HD 75289 (central bright star) from 2MASS (02/99) ( top) and our first epoch NTT/SofI image (01/02) ( bottom). The total integration time is 10 min. The co-moving companion is located 21.5 arcsec east of HD 75289 and is also visible in the 2MASS image (marked object). The stars R1 and R2 are used as comparison stars in Fig. 4.
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In the text

$\begin{figure} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig2.eps}}\end{figure}$ Figure 2: Result of the astrometry obtained by comparing two NTT images from epochs 01/02 and 12/02. The formal proper motions of all detected objects around HD 75289 A are shown in the diagram. All of them have negligible proper motions, similar in size to the astrometric uncertainty ( $\sim$ 20 mas) hence they are very slowly moving background objects. Only HD 75289 B (bottom with error bars) shares the proper motion of HD 75289 A (square) which is well known from the Hipparcos astrometry. The proper motion of the bright primary star A is not measured in our NTT images because of saturation.
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In the text

$\begin{figure} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig3.eps}}\vs... ....2mm} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig4.eps}}\end{figure}$ Figure 3: Proper motion of HD 75289 B for all three epochs. We measure the distance between R1 and HD 75289 B ( top) and the position angle PA of HD 75289 B measured from R2. See Fig. 1 for the stars R1 and R2. Due to the motion of HD 75289 B relative to the reference stars both values are changing following the predicted curves (straight lines) for a co-moving companion to HD 752898 A. The astrometric uncertainty is illustrated with dotted lines.
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In the text

$\begin{figure} \par\resizebox{8.2cm}{!}{\includegraphics[clip]{1009fig5.eps}}\end{figure}$ Figure 4: Relative flux of HD 75289 A and B. The drop at 1.85 $\mu$ m is due to strong water absorption as well as some telluric lines. From a black body fit, we derive a $T_{\rm eff}$ of the companion between 3250 K and 3500 K, in agreement with a spectral type M 2 to M 5.
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In the text

$\begin{figure} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig6.eps}}\vs... ....6mm} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig7.eps}}\end{figure}$ Figure 5: Normalized H and K band spectra of HD 75289 B, compared with spectra of GJ 411 (M 2+V), GJ 725 (M3V) and Wolf 359 (M6V) from Meyer et al. (1997/98).
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In the text

$\begin{figure} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig8.eps}}\end{figure}$ Figure 6: The color-magnitude diagram with the isochrone for 5 Gyr from Baraffe et al. (1998) with [M/H] = 0, mixing length parameter $\alpha =1$ and He abundance Y=0.25. The primary and its companion are included in the diagram with their uncertainties in magnitude and color. Masses are indicated as numbers in solar masses.
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In the text

$\begin{figure} \par\resizebox{8.2cm}{!}{\includegraphics[clip]{1009fig9.eps}}\end{figure}$ Figure 7: The limiting H magnitude versus separation from HD 75289 A for our NTT image shown in Fig. 1 and 2MASS. The corresponding projected separation in AU is shown on the upper x-axis. Saturation occurs within 1.5 arcsec (43 AU) (see vertical dashed line) hence a companion search is impossible there. The detection of all stellar companions is feasible beyond 4.7 arcsec (136 AU). The right y-scale shows the predicted absolute H magnitudes for substellar objects from Baraffe et al. (2003) models for an age of 5 Gyr. The 3 $\sigma$ detection limit is 19 mag in H, hence substellar companions down to 0.050 $M_{\odot }$ can be found beyond 15 arcsec (434 AU).
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In the text

$\begin{figure} \par\resizebox{6.5cm}{!}{\includegraphics[clip]{1009fig1.eps}}\end{figure}$	Figure 1: H band images of HD 75289 (central bright star) from 2MASS (02/99) ( top) and our first epoch NTT/SofI image (01/02) ( bottom). The total integration time is 10 min. The co-moving companion is located 21.5 arcsec east of HD 75289 and is also visible in the 2MASS image (marked object). The stars R1 and R2 are used as comparison stars in Fig. 4.
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$\begin{figure} \par\resizebox{8.2cm}{!}{\includegraphics[clip]{1009fig5.eps}}\end{figure}$	Figure 4: Relative flux of HD 75289 A and B. The drop at 1.85 $\mu$ m is due to strong water absorption as well as some telluric lines. From a black body fit, we derive a $T_{\rm eff}$ of the companion between 3250 K and 3500 K, in agreement with a spectral type M 2 to M 5.
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$\begin{figure} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig6.eps}}\vs... ....6mm} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig7.eps}}\end{figure}$	Figure 5: Normalized H and K band spectra of HD 75289 B, compared with spectra of GJ 411 (M 2+V), GJ 725 (M3V) and Wolf 359 (M6V) from Meyer et al. (1997/98).
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$\begin{figure} \par\resizebox{8.4cm}{!}{\includegraphics[clip]{1009fig8.eps}}\end{figure}$	Figure 6: The color-magnitude diagram with the isochrone for 5 Gyr from Baraffe et al. (1998) with [M/H] = 0, mixing length parameter $\alpha =1$ and He abundance Y=0.25. The primary and its companion are included in the diagram with their uncertainties in magnitude and color. Masses are indicated as numbers in solar masses.
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