Discovery of a Bright Field Methane (T-type) Brown Dwarf by 2MASS

Adam J. Burgasser1, John C. Wilson2, J. Davy Kirkpatrick3, Michael F. Skrutskie4, Michael R.
Colonno2, Alan T. Enos2, J.D. Smith2, Charles P. Henderson2, John E. Gizis3, Michael E.
Brown5,6, James R. Houck2


      We report the discovery of a bright (J= 13.83 +/- 0.03) methane brown dwarf, or T dwarf, by the Two Micron All Sky Survey. This object, 2MASSI J0559191-140448, is the first brown dwarf identified by the newly commissioned CorMASS instrument mounted on the Palomar 60-inch Telescope. Near-infrared spectra from 0.9-2.35mm show characteristic CH4 bands at 1.1, 1.3, 1.6, and 2.2mm, which are significantly shallower than those seen in other T dwarfs discovered to date. Coupled with the detection of an FeH band at 0.9896 and two sets of K I doublets at J-band, we propose that 2MASS J0559-14 is a warm T dwarf, close to the transition between L and T spectral classes. The brightness of this object makes it a good candidate for detailed investigation over a broad wavelength regime and at higher resolution.

Subject headings: infrared: stars - stars: individual (2MASSI J0559191-140448) -
stars: fundamental parameters - stars: low mass, brown dwarfs

     1   Division of Physics, M/S 103-33, California Institute of Technology, Pasadena, CA 91125;

     2   Space Sciences, Cornell University, Ithaca, NY 14853;,,,,,

     3   Infrared Processing and Analysis Center, M/S 100-22, California Institute of Technology, Pasadena, CA 91125;,

     4   Five College Astronomy Department, Department of Physics and Astronomy, University of Massachusetts, Amherst, MA 01003;

     5   Division of Geological and Plantary Sciences, M/S 105-21, California Institute of Technology, Pasadena, CA 91125;

     6   Alfred P. Sloan Research Fellow

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Tentatively scheduled for publication in the August 2000 Astronomical Journal