2001/05/10 by Matthew A. Kenworthy, M. A. Kenworthy, Karl-Heinz Hofmann +18 · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/320934
published as Astrophys.J.554:L67-L70,2001 · 17 pages, 3 figures, 2 tables, accepted by ApJ Letters. Version with high-res fig. 1 available at http://focus.as.arizona.edu/~mak/gl569b/
arxiv created 2001/05/10 · openalex publication_date 2001/06/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double with separation ~1 AU. To explore the orbital motion and masses, we have undertaken a high-resolution (~0 05) astrometric study. Images were obtained over 1.5 yr with bispectrum speckle interferometry at the 6.5 m Multiple Mirror Telescope (MMT) and 6 m Special Astrophysical Observatory telescope. Our data show motion corresponding to more than half the orbital period and constrain the total mass to be greater than 0.115 M ☉ , with a most probable value of 0.145 M ☉ . Higher masses cannot be excluded without more extended observations, but from statistical analysis we find an 80% probability that the total mass is less than 0.21 M ☉ . An infrared spectrum of the blended B double obtained with the MMT has been modeled as a blend of two different spectral types, chosen to be consistent with the measured J - and K -band brightness difference of a factor of ~2. The blended fit is not nearly as good as that to a pure M8.5+ template. Therefore, we hypothesize that the brighter component likely has two unresolved components with near equal masses, each the same as the fainter component. If Gl 569B is a triple, our dynamical limits suggest each component has a mass of 50 M Jup . We infer an age for the system of 300 Myr from its kinematic motion, which places it as a member of the Ursa Major moving group. All the above parameters are consistent with the latest DUSTY evolution models for brown dwarfs.