• DOI:10.1088/0004-637X/762/2/119
• Corpus ID: 42923100

PARALLAXES AND PROPER MOTIONS OF ULTRACOOL BROWN DWARFS OF SPECTRAL TYPES Y AND LATE T

@article{Marsh2012PARALLAXESAP,
  title={PARALLAXES AND PROPER MOTIONS OF ULTRACOOL BROWN DWARFS OF SPECTRAL TYPES Y AND LATE T},
  author={K A Marsh and Edward L. Wright and J. Davy Kirkpatrick and Christopher Ryan Gelino and Michael C. Cushing and Roger L. Griffith and Michael F. Skrutskie and Peter Eisenhardt},
  journal={The Astrophysical Journal},
  year={2012},
  volume={762}
}

• K. Marsh, E. Wright, +5 authors P. Eisenhardt
• Published 29 November 2012
• Physics, Geology
• The Astrophysical Journal

We present astrometric measurements of 11 nearby ultracool brown dwarfs of spectral types Y and late-T, based on imaging observations from a variety of space-based and ground-based telescopes. These measurements have been used to estimate relative parallaxes and proper motions via maximum likelihood fitting of geometric model curves. To compensate for the modest statistical significance (≲ 7) of our parallax measurements we have employed a novel Bayesian procedure for distance estimation which makes use of an a priori distribution of tangential velocities, Vtan, assumed similar to that implied by previous observations of T dwarfs. Our estimated distances are therefore somewhat dependent on that assumption. Nevertheless, the results have yielded distances for five of our eight Y dwarfs and all three T dwarfs. Estimated distances in all cases are ≳ 3 pc. In addition, we have obtained significant estimates of Vtan for two of the Y dwarfs; both are <100 km s−1, consistent with membership in the thin disk population. Comparison of absolute magnitudes with model predictions as a function of color shows that the Y dwarfs are significantly redder in J − H than predicted by a cloud-free model.