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Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T

Marsh, Kenneth A. and Wright, Edward L. and Kirkpatrick, J. Davy and Gelino, Christopher R. and Cushing, Michael C. and Griffith, Roger L. and Skrutskie, Michael F. and Eisenhardt, Peter R. (2013) Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T. Astrophysical Journal, 762 (2). Art. No. 119. ISSN 0004-637X.

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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, V_tan, 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 V_tan 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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Marsh, Kenneth A.0000-0003-0107-7803
Wright, Edward L.0000-0001-5058-1593
Kirkpatrick, J. Davy0000-0003-4269-260X
Cushing, Michael C.0000-0001-7780-3352
Additional Information:© 2013 American Astronomical Society. Received 2012 May 4; accepted 2012 November 22; published 2012 December 21. We thank C. Morley for providing the results of model calculations and also the referee for very helpful comments. This publication makes use of data products from the Widefield Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued to programs 70062 and 80109 by JPL/Caltech. Thiswork is also based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 12330, support for which was provided by NASA through a grant from the Space Telescope Science Institute. This paper also includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. This research has made use of the NASA/IPAC Infrared Science Archive (IRSA), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and also the SIMBAD database, operated at CDS, Strasbourg, France.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Space Telescope Science InstituteUNSPECIFIED
NASANAS 5-26555
Subject Keywords:astrometry; brown dwarfs; stars: low-mass
Issue or Number:2
Record Number:CaltechAUTHORS:20130204-113953004
Persistent URL:
Official Citation:Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T Kenneth A. Marsh et al. 2013 ApJ 762 119
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36756
Deposited By: Jason Perez
Deposited On:05 Feb 2013 15:34
Last Modified:09 Mar 2020 13:19

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