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The Physical Properties of Four ~600 K T Dwarfs

Leggett, S. K. and Cushing, Michael C. and Saumon, D. and Marley, M. S. and Roellig, T. L. and Warren, S. J. and Burningham, Ben and Jones, H. R. A. and Kirkpatrick, J. D. and Lodieu, N. and Lucas, P. W. and Mainzer, A. K. and Martín, E. L. and McCaughrean, M. J. and Pinfield, D. J. and Sloan, G. C. and Smart, R. L. and Tamura, M. and Van Cleve, J. (2009) The Physical Properties of Four ~600 K T Dwarfs. Astrophysical Journal, 695 (2). pp. 1517-1526. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20090901-133952369

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Abstract

We present Spitzer 7.6-14.5 μm spectra of ULAS J003402.77–005206.7 and ULAS J133553.45+113005.2, two T9 dwarfs with the latest spectral types currently known. We fit synthetic spectra and photometry to the near- through mid-infrared energy distributions of these dwarfs and that of the T8 dwarf 2MASS J09393548–2448279. We also analyze near-infrared data for another T9, CFBD J005910.82–011401.3. We find that the ratio of the mid- to near-infrared fluxes is very sensitive to effective temperature at these low temperatures, and that the 2.2 μm and 4.5 μm fluxes are sensitive to metallicity and gravity; increasing gravity has a similar effect to decreasing metallicity, and vice versa, and there is a degeneracy between these parameters. The 4.5 μm and 10 μm fluxes are also sensitive to vertical transport of gas through the atmosphere, which we find to be significant for these dwarfs. The full near- through mid-infrared spectral energy distribution allows us to constrain the effective temperature (K)/gravity (ms^(–2))/metallicity ([m/H] dex) of ULAS J0034–00 and ULAS J1335+11 to 550-600/100-300/0.0-0.3 and 500-550/100-300/0.0-0.3, respectively. These fits imply low masses and young ages for the dwarfs of 5-20 M_(Jupiter) and 0.1-2 Gyr. The fits to 2MASS J0939–24 are in good agreement with the measured distance, the observational data, and the earlier T8 near-infrared spectral type if it is a slightly metal-poor 4-10 Gyr old system consisting of a 500 K and 700 K, ~25 M_(Jupiter) and ~40 M_(Jupiter), pair, although it is also possible that it is an identical pair of 600 K, 30_(M Jupiter), dwarfs. As no mid-infrared data are available for CFBD J0059–01 its properties are less well constrained; nevertheless it appears to be a 550-600 K dwarf with g = 300-2000 ms^(–2) and [m/H] = 0-0.3 dex. These properties correspond to mass and age ranges of 10-50 M_(Jupiter) and 0.5-10 Gyr for this dwarf.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/695/2/1517DOIArticle
http://www.iop.org/EJ/abstract/0004-637X/695/2/1517/PublisherArticle
ORCID:
AuthorORCID
Cushing, Michael C.0000-0001-7780-3352
Marley, M. S.0000-0002-5251-2943
Kirkpatrick, J. D.0000-0003-4269-260X
Smart, R. L.0000-0002-4424-4766
Tamura, M.0000-0002-6510-0681
Additional Information:© 2009 The American Astronomical Society. Received 2008 December 9; accepted 2009 January 28; published 2009 April 7. This work is based 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 by JPL/Caltech. S.K.L.’s research is supported by the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., on behalf of the international Gemini partnership of Argentina, Australia, Brazil, Canada, Chile, the United Kingdom, and the United States of America. E.L.M.’s research is supported by The Spanish Ministry of Science via project AYA2007-67458.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
Ministerio de Educación y Ciencia (MEC)AYA2007-67458
Subject Keywords:stars: atmospheres; stars: individual (ULAS J003402.77-005206.7, ULAS J133553.45+113005.2, 2MASS J09393548-2448279, CFBD J005910.82-011401.3); stars: low-mass, brown dwarfs
Issue or Number:2
Record Number:CaltechAUTHORS:20090901-133952369
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20090901-133952369
Official Citation:The Physical Properties of Four ~600 K T Dwarfs S. K. Leggett, Michael C. Cushing, D. Saumon, M. S. Marley, T. L. Roellig, S. J. Warren, Ben Burningham, H. R. A. Jones, J. D. Kirkpatrick, N. Lodieu, P. W. Lucas, A. K. Mainzer, E. L. Martín, M. J. McCaughrean, D. J. Pinfield, G. C. Sloan, R. L. Smart, M. Tamura, and J. Van Cleve 2009 ApJ 695 1517-1526 doi: 10.1088/0004-637X/695/2/1517.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15529
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:14 Sep 2009 19:19
Last Modified:09 Mar 2020 13:19

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