2012ApJ...744..120E

We present the results of an aperture-masking interferometry survey for substellar companions around 67 members of the young (∼8-200 Myr) nearby (∼5-86 pc) AB Doradus, β Pictoris, Hercules-Lyra, TW Hya, and Tucana-Horologium stellar associations. Observations were made at near-infrared wavelengths between 1.2 and 3.8 µm using the adaptive optics facilities of the Keck II, Very Large Telescope UT4, and Palomar Hale Telescopes. Typical contrast ratios of ∼100-200 were achieved at angular separations between ∼40 and 320 mas, with our survey being 100% complete for companions with masses below ∼0.25 M _☉ across this range. We report the discovery of a 0.52±0.09 M _☉ companion to HIP 14807, as well as the detections and orbits of previously known stellar companions to HD 16760, HD 113449, and HD 160934. We show that the companion to HD 16760 is in a face-on orbit, resulting in an upward revision of its mass from M₂ sin i ∼ 14 M_Jto M₂= 0.28 ±0.04 M_☉. No substellar companions were detected around any of our sample members, despite our ability to detect companions with masses below 80 M_J for 50 of our targets: of these, our sensitivity extended down to 40 M_J around 30 targets, with a subset of 22 subject to the still more stringent limit of 20 M_J. A statistical analysis of our non-detection of substellar companions allows us to place constraints on their frequency around ∼0.2-1.5 M_☉stars. In particular, considering companion mass distributions that have been proposed in the literature, we obtain an upper limit estimate of ∼9%-11% for the frequency of 20-80 M_Jcompanions between 3 and 30 AU at 95% confidence, assuming that their semimajor axes are distributed according to d{N}/da ∝a^–1 in this range.