The star-forming regions in Chamaeleon are one of the nearest (distance ~165
pc) and youngest (age ~2 Myrs) conglomerates of recently formed stars and the
ideal target for population studies of star formation. We investigate a total
of 16 Cha targets, which have been suggested, but not confirmed as binaries or
multiple systems in previous literature. We used the adaptive optics instrument
Naos-Conica (NACO) at the Very Large Telescope Unit Telescope 4 of the Paranal
Observatory, at 2-5 different epochs, in order to obtain relative and absolute
astrometric measurements, as well as differential photometry in the J, H, and K
band. On the basis of known proper motions and these observations, we analyse
the astrometric results in our "Proper Motion Diagram" (PMD: angular separation
/ position angle versus time), to eliminate possible (non-moving) background
stars, establish co-moving binaries and multiples, and search for curvature as
indications for orbital motion. All previously suggested close components are
co-moving and no background stars are found. The angular separations range
between 0.07 and 9 arcseconds, corresponding to projected distances between the
components of 6-845 AU. Thirteen stars are at least binaries and the remaining
three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order
multiple systems with up to four components. In 13 cases, we found significant
slopes in the PMDs, which are compatible with orbital motion whose periods
range from 60 to 550 years. However, in only four cases there are indications
of a curved orbit, the ultimate proof of a gravitational bond. Massive primary
components appear to avoid the simultaneous formation of equal-mass secondary
components. (abridged)Comment: 33 pages, 22 figures, accepted for publication in A&A, 2nd version:
typos and measurement unit added in Table
