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Published January 10, 2012 | Published
Journal Article Open

Mapping the Shores of the Brown Dwarf Desert. III. Young Moving Groups


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 M_2 sin i ~ 14 M_J to M_2 = 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_J companions between 3 and 30 AU at 95% confidence, assuming that their semimajor axes are distributed according to dN/da ∝ a^(-1) in this range.

Additional Information

© 2012 American Astronomical Society. Received 2011 January 18; accepted 2011 September 26; published 2011 December 20. M.I. was the recipient of the Australian Research Council postdoctoral fellowship (project number DP0878674). A.K. was previously supported by a NASA/Origins grant to Lynne Hillenbrand and is currently supported by a NASA Hubble Fellowship grant. This work was also partially supported by the National Science Foundation under Grant Numbers 0506588 and 0705085. This work made use of data products from 2MASS, which is a joint project of the University of Massachusetts and IPAC/Caltech, funded by NASA and the NSF. Our research has also made use of the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station (http://www.nofs.navy.mil/data/fchpix/). This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. We recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Published - Evans2012p16941Astrophys_J.pdf


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