High-precision Radio and Infrared Astrometry of LSPM J1314+1320AB. I. Parallax, Proper Motions, and Limits on Planets

Author(s): Jan Forbrich, Trent J. Dupuy, Mark J. Reid, Edo Berger, Aaron Rizzuto
Abstract: We present multi-epoch astrometric radio observations with the Very Long Baseline Array (VLBA) of the young ultracool-dwarf binary LSPM J1314+1320AB. The radio emission comes from the secondary star. Combining the VLBA data with Keck near-infrared adaptive-optics observations of both components, a full astrometric fit of parallax (π abs = 57.975 ± 0.045 mas, corresponding to a distance of d = 17.249 ± 0.013 pc), proper motion (μ αcos δ = -247.99 ± 0.10 mas yr^-1, μ_δ = -183.58 ± 0.22 mas yr^-1), and orbital motion is obtained. Despite the fact that the two components have nearly identical masses to within ±2%, the secondary’s radio emission exceeds that of the primary by a factor of ≳30, suggesting a difference in stellar rotation history, which could result in different magnetic field configurations. Alternatively, the emission could be anisotropic and beamed toward us for the secondary but not for the primary. Using only reflex motion, we exclude planets of mass 0.7-10 M_jup with orbital periods of 600-10 days, respectively. Additionally, we use the full orbital solution of the binary to derive an upper limit for the semimajor axis of 0.23 au for stable planetary orbits within this system. These limits cover a parameter space that is inaccessible with, and complementary to, near-infrared radial velocity surveys of ultracool dwarfs. Our absolute astrometry will constitute an important test for the astrometric calibration of Gaia.
Organisation(s): Department of Astrophysics
External organisation(s): Harvard-Smithsonian Center for Astrophysics, University of Texas, Austin
Journal: The Astrophysical Journal
Volume: 827
No. of pages: 8
ISSN: 0004-637X
DOI: https://doi.org/10.3847/0004-637X/827/1/22
Publication date: 08-2016
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/af21c08a-9bdb-4010-b83b-46ebff6240a4

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