All Figures

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_1.eps} } \end{figure}$ Figure 1: Left: the SofI small field image of the planet host star HD 114729 (central bright star with diffraction spikes and reflections), taken in June 2003 in the H band. The total integration time is 10 min. Several faint companion-candidates can be seen. Right: magnified image of the central part of the FOV with different cuts. A companion-candidate, located $\sim$ 8 arcsec northwest of the central star, is visible.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_2.eps} } \end{figure}$ Figure 2: The separation and the position angle between HD 114729 B and its primary in the 2MASS image (epoch 04/99) and our SofI images from epoch 12/02 and 06/03. If HD 114729 B is a non-moving background star, both parameters must change due to the well-known proper and parallactic motion of the primary star which is illustrated with a solid line. However, the measured separation and position angle are constant. With the given astrometric uncertainties the background hypothesis can be rejected at a 10 $\sigma$ level in separation and at a 15 $\sigma$ level in position angle. Hence, HD 114729 B is clearly co-moving with the exoplanet host star HD 114729 A.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_3.eps} } \end{figure}$ Figure 3: The derived proper motion of all companion candidates detected in our NTT images ( ${\it S/N}>10$ ) from epochs 12/02 and 06/03. The expected proper motion of the primary is derived from Hipparcos data and is shown as a small square in the plot (A). HD 114729 B clearly shares the proper motion of the exoplanet host star. All other detected companion-candidates prove to be non-moving background stars.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_4.eps} } \end{figure}$ Figure 4: Left: the SofI small field image of the planet host star HD 196050, obtained in epoch 06/03 in H band. The total integration is 10 min. Several faint companion-candidates are detected. Right: image of the central region of the field. The co-moving companion, HD 196050 B is located $\sim$ 11 arcsec south of its primary star.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_5.eps} } \end{figure}$ Figure 5: Separation and position angle of HD 196050 B to its primary for the 2MASS image (epoch 06/00) and our SofI images (epoch 06/03 and 07/04). The expected variation of both parameters if HD 196050 B was a non-moving object is illustrated with a solid line. The separation and the position angle are constant within the astrometric uncertainty, as it is expected for a co-moving companion and significantly (11 $\sigma$ in position angle) different from the expected values for a non-moving HD 196050 B.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_6.eps} } \end{figure}$ Figure 6: The derived proper motion of all detected companion candidates ( ${\it S/N}>10$ ) shown in Fig. 4 for our two SofI images taken in epoch 06/03 and 07/04. The expected proper motion of the primary is derived with the well-known proper and parallactic motion of the primary (from Hipparcos data) and is shown as a small square in the plot (A). HD 196050 B is clearly co-moving to the exoplanet host star, but all other detected companion-candidates emerge as non-moving background stars.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_7.eps} } \end{figure}$ Figure 7: The SofI small field image of the exoplanet host star HD 213240. It was taken in July 2004 in H band with a total integration of 10 min. Only two companion-candidates both are marked in the image are detected with ${\it S/N}\geq 10$ and offer a sufficient astrometry to check common proper motion with the bright primary. The separation of both companion-candidates to HD 213240 varies over time as expected from the well-known proper and parallactic motion of the exoplanet host star, hence they are non-moving background stars.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_8.eps} } \end{figure}$ Figure 8: The SofI large field H band image of HD 213240 taken in July 2004. The total integration time is 7 min. Several companion-candidates are detected. An arrow points to the co-moving companion HD 213240 C which was detected by comparing this SofI image with the image from the 2MASS survey.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_9.eps} } \end{figure}$ Figure 9: The separation and the position angle between HD 213240 C and its primary for the 2MASS image (epoch 08/99) and our first epoch SofI large field image (epoch 07/04). Separation and position angle are constant in both observing epochs typical for a co-moving object. Furthermore if HD 213240 C would be non-moving the position angle must significantly change following the well-known proper and parallactic motion of HD 213240 A (see solid lines).
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_10.eps} } \end{figure}$ Figure 10: Left: the UFTI H band image obtain in October 2003. The integration time is 9.6 min. Two companion-candidates are detected with good astrometry precision both indicated with markers. Right: the central part of the image zoomed and rescaled. The newly found co-moving companion HD 16141 B is visible $\sim$ 6 arcsec south of the exoplanet planet host.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_11.eps} } \end{figure}$ Figure 11: The separation and the position angle of HD 16141 B both UFTI/UKIRT images (epoch 11/02 and 10/03). Separation and position angle are constant in both observing epochs as expected for a co-moving companion and are significantly different to the expected values if HD 16141 B was a non-moving background object using the well-known proper and parallactic motion of the primary (see solid lines).
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_12.eps} } \end{figure}$ Figure 12: A color-magnitude diagram of all detected companions for which J, H and Ks infrared magnitudes are known. A isochrone from Baraffe et al. (1998) models is illustrated as solid line with dots which show the companion-mass in units of solar mass. All companions are consistent with low-mass stellar objects at the distance of the primaries. In addition we also show HD 75289 B from Mugrauer et al. (2004a).
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_13.eps} } \end{figure}$ Figure 13: K band SofI spectra of the detected companions HD 114729 B, HD 196050 B and HD 213240 C. Furthermore we show comparison spectra of spectral type M1V and M3V. The arrow indicate telluric features.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{2297_14.eps}\end{figure}$ Figure 14: The updated mass-period ( upper panel) and eccentricity-period distribution ( lower panel) of Eggenberger et al. (2004). All new binary-star planets are marked with black squares and all binary-star planets from Eggenberger et al. (2004) are shown with dark dots. HD 213240 b, HD 196050 b, and HD 114729 b exhibit minimum masses smaller 5 $M_{\rm Jup}$ comparable to all other binary-star planets found with periods longer than 100 days. However with $M\sin(i)=7.2~M_{\rm Jup}$ HD 89744 b is the first known exception from that rule. HD 75289 b exhibits a low eccentricity consistent with all other known binary-star planets on orbits shorter 40 days. The eccentricities of HD 213240 b, HD 196050 b, HD 114729 b and HD 89744 b are widely spread from 0.19 up to 0.7, consistent with the eccentricity distribution of other long periodic binary-star as well as single-star planets. The eccentricity distribution of both exoplanet populations seems to be similar for orbital periods longer than 100 days.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_15.eps} }\end{figure}$ Figure 15: Detection limit of SofI large field in H band for a range of separation given in arcsec at the bottom and as projected separation in AU at the top. At $\sim$ 1 arcsec saturation occurs (doted line). All stellar companions ( $m~\ge~0.075$ $M_{\odot }$ ) are detectable beyond the distance illustrated by the straight line.
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In the text

$\begin{figure} \par {\includegraphics[width=8.35cm,clip]{2297_16.eps} }\end{figure}$ Figure 16: Detection limits of SofI small field and UFTI images in H band for a range of separations given in arcsec at the bottom and as projected separation in AU at the top of each individual plot. At $\sim$ 1 arcsec saturation occurs (doted line). All stellar companions ( $m~\ge~0.075$ $M_{\odot }$ ) are detectable beyond the distance illustrated by the straight lines in each individual plot.
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In the text

$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_4.eps} } \end{figure}$	Figure 4: Left: the SofI small field image of the planet host star HD 196050, obtained in epoch 06/03 in H band. The total integration is 10 min. Several faint companion-candidates are detected. Right: image of the central region of the field. The co-moving companion, HD 196050 B is located $\sim$ 11 arcsec south of its primary star.
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$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_8.eps} } \end{figure}$	Figure 8: The SofI large field H band image of HD 213240 taken in July 2004. The total integration time is 7 min. Several companion-candidates are detected. An arrow points to the co-moving companion HD 213240 C which was detected by comparing this SofI image with the image from the 2MASS survey.
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$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_10.eps} } \end{figure}$	Figure 10: Left: the UFTI H band image obtain in October 2003. The integration time is 9.6 min. Two companion-candidates are detected with good astrometry precision both indicated with markers. Right: the central part of the image zoomed and rescaled. The newly found co-moving companion HD 16141 B is visible $\sim$ 6 arcsec south of the exoplanet planet host.
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$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_13.eps} } \end{figure}$	Figure 13: K band SofI spectra of the detected companions HD 114729 B, HD 196050 B and HD 213240 C. Furthermore we show comparison spectra of spectral type M1V and M3V. The arrow indicate telluric features.
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$\begin{figure} \par {\includegraphics[width=8.2cm]{2297_15.eps} }\end{figure}$	Figure 15: Detection limit of SofI large field in H band for a range of separation given in arcsec at the bottom and as projected separation in AU at the top. At $\sim$ 1 arcsec saturation occurs (doted line). All stellar companions ( $m~\ge~0.075$ $M_{\odot }$ ) are detectable beyond the distance illustrated by the straight line.
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