2007/02/01 by Nick Siegler, Laird M. Close, Adam J. Burgasser +4 · 48 citations
Physics and Astronomy · #Adaptive optics #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Binary number #Brown dwarf #Laser guide star #Mass ratio #Physics #Proper motion #Stars #Stellar, planetary, and galactic studies #Telescope #astro-ph
paper · pdf · doi:10.1086/513273
published in The Astronomical Journal 133(5), 2320-2326 (Institute of Physics) · 10 pages, 3 figures; accepted for publication to AJ
arxiv created 2007/02/01 · openalex publication_date 2007/04/04 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present the discovery of 2MASS J21321145+1341584AB as a closely separated (0.066''), very low mass field dwarf binary, resolved in the near-infrared by the Keck II telescope using laser guide star adaptive optics. Physical association is deduced from the angular proximity of the components and constraints on their common proper motion. We have obtained a near-infrared spectrum of the binary and find that it is best described by an L5 ± 0.5 primary and an L7.5 ± 0.5 secondary. Model-dependent masses predict that the two components straddle the hydrogen-burning limit threshold, with the primary likely stellar and the secondary likely substellar. The properties of this system—close projected separation (1.8 ± 0.3 AU) and near-unity mass ratio—are consistent with previous results for very low mass field binaries. The relatively short estimated orbital period of this system (∼7-12 yr) makes it a good target for dynamical mass measurements. It is interesting to note that the system's angular separation is the tightest yet for any very low mass binary published from a ground-based telescope and that it is the tightest binary discovered with laser guide star adaptive optics to date.