Located at ~2pc, the L7.5+T0.5 dwarfs system WISE J104915.57-531906.1 (Luhman16AB) is the third closest system known to Earth, making it a key benchmark for detailed investigation of brown dwarf atmospheric properties, thermal evolution, multiplicity, and planet-hosting frequency. In the first study of this series -- based on a multi-cycle Hubble Space Telescope (HST) program -- we provide an overview of the project and present improved estimates of positions, proper motions, annual parallax, mass ratio, and the current best assessment of the orbital parameters of the A-B pair. Our HST observations encompass the apparent periastron of the binary at 220.5+/-0.2 mas at epoch 2016.402. Although our data seem to be inconsistent with recent ground-based astrometric measurements, we also exclude the presence of third bodies down to Neptune masses and periods longer than a year.
@article{arxiv.1706.00657,
title = {Hubble Space Telescope astrometry of the closest brown dwarf binary system -- I. Overview and improved orbit},
author = {L. R. Bedin and D. Pourbaix and D. Apai and A. J. Burgasser and E. Buenzli and H. M. J. Boffin and M. Libralato},
journal= {arXiv preprint arXiv:1706.00657},
year = {2017}
}
Comments
19 pages, 9 figures, 9 tables. Accepted for publication in MNRAS on 2017 May 9