HIGH-PRECISION RADIO AND INFRARED ASTROMETRY OF LSPM J1314+1320AB. I. PARALLAX, PROPER MOTIONS, AND LIMITS ON PLANETS
- University of Vienna, Department of Astrophysics, Türkenschanzstr. 17, A-1180 Vienna (Austria)
- The University of Texas at Austin, Department of Astronomy, 2515 Speedway C1400, Austin, TX 78712 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
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 {sub abs} = 57.975 ± 0.045 mas, corresponding to a distance of d = 17.249 ± 0.013 pc), proper motion (μ {sub α} {sub cos} {sub δ} = −247.99 ± 0.10 mas yr{sup −1}, μ {sub δ} = −183.58 ± 0.22 mas yr{sup −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 {sub 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 .
- OSTI ID:
- 22667534
- Journal Information:
- Astrophysical Journal, Vol. 827, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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