All Figures

Figure 1: Examples of multiepoch astrometry for three true companions ( two upper lines) and for three companion candidates which are background stars ( two lower lines). For each companion candidate, the upper panel shows the evolution of angular separation versus time and the lower panel shows the evolution of position angle versus time. Solid lines take into account the primary proper and parallactic motions, and thus depict the evolution expected for background objects with negligible proper motion. The grey zones represent the associated uncertainties, which comprise uncertainties on the parallax and on the proper motion of the primary star, along with the uncertainty on the first-epoch measurement.

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In the text

Figure 2: Near-infrared color-magnitude diagrams for the 21 companion candidates with the most precise colors (uncertainties on apparent magnitudes less than 0.15). Dots and solid error bars denote true or likely bound companions, open circles and dashed error bars denote candidates with an unknown companionship status, while dots and dotted error bars denote unbound objects. These diagrams are based on our own photometric data, except for HD 46375, HD 134180, and HD 223913 for which we used the 2MASS photometry. For comparison, we also show main-sequence F7-K stars from Halbwachs et al. (2003) and Eggenberger et al. (2004a) (open triangles), M dwarfs from Delfosse and coworkers (open circles; Delfosse & Forveille, private communication), and L dwarfs from Vrba et al. (2004). Known binaries have been removed from the samples of G, K, and M stars. The solid line is a typical evolutionary model from Baraffe et al. (1998) (solar metallicity, t = 5 Gyr, mixing length of one pressure scale height for masses below 0.7 , and of 1.9 scale height for higher masses). The reference photometric system is 2MASS and conversions were made whenever required.

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In the text

Figure 5: Survey sensitivity and detected sources in the H (left) and K (right) bands. Dots represent bound and likely bound companions, open circles represent unbound and likely unbound companion candidates, while crosses denote companion candidates with an unknown companionship status. Labels on the right-hand side of each plot indicate the relationship between magnitude (NACO photometric system) and spectral type for companions to a typical K0 star. Solid lines are median sensitivity limits obtained with the two consecutive detectors of CONICA. The best detection curves in the external region dominated by readout noise are those obtained with the new Aladdin3 detector.

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In the text

Figure 3: Multiepoch astrometry for the true and likely bound companions. For each companion candidate, the upper panel shows the evolution of angular separation versus time, and the lower panel the evolution of position angle versus time. Solid lines take into account the primary proper and parallactic motions, and thus depict the evolution expected for background objects with negligible proper motion. The grey zones represent the associated uncertainties, which comprise uncertainties on the parallax and on the proper motion of the primary star, along with the uncertainty on the first-epoch measurement. Our own data points are represented by dots, while additional measurements from the literature (see the notes for references) are represented by crosses.

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In the text

	Figure 3: continued.
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In the text

	Figure 3: continued.
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In the text

	Figure 3: continued.
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In the text

	Figure 4: NACO images of the true and likely bound companions. Note that the NB_1.64 filter produces several bright ghosts surrounding the image of the main target.
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In the text

	Figure 4: continued.
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In the text