Discovery of a new companion and evidence of a circumprimary disk: Adaptive optics imaging of the young multiple system VW Chamaeleon

Since a majority of young low-mass stars are members of multiple systems, t he study of their stellar and disk configurations is crucial to our underst anding of both star and planet formation processes. Here we present near-in frared adaptive optics observations of the young multiple star system VW Ch amaeleon. The previously known 0 " .7 binary is clearly resolved already in our raw J- and K-band images. We report the discovery of a new faint compa nion to the secondary, at an apparent separation of only 0 " .1, or 16 AU. Our high-resolution photometric observations also make it possible to measu re the J-K colors of each of the three components individually. We detect a n infrared excess in the primary, consistent with theoretical models of a c ircumprimary disk. Analytical and numerical calculations of orbital stabili ty show that VW Cha may be a stable triple system. Using models for the age and total mass of the secondary pair, we estimate the orbital period to be 74 yr. Thus, follow-up astrometric observations might yield direct dynamic al masses within a few years and constrain evolutionary models of low-mass stars. Our results demonstrate that adaptive optics imaging in conjunction with deconvolution techniques is a powerful tool for probing close multiple systems.