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Title:
The First Substellar Subdwarf? Discovery of a Metal-poor L Dwarf with Halo Kinematics
Authors:
Burgasser, Adam J.; Kirkpatrick, J. Davy; Burrows, Adam; Liebert, James; Reid, I. Neill; Gizis, John E.; McGovern, Mark R.; Prato, L.; McLean, Ian S.
Affiliation:
AA(Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 , , , .; Hubble Fellow.), AB(Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125; .), AC(Steward Observatory, University of Arizona, Tucson, AZ 85721; , .), AD(Steward Observatory, University of Arizona, Tucson, AZ 85721; , .), AE(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; .), AF(Department of Physics and Astronomy, University of Delaware, Newark, DE 19716; .), AG(Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 , , , .), AH(Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 , , , .), AI(Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 , , , .)
Publication:
The Astrophysical Journal, Volume 592, Issue 2, pp. 1186-1192. (ApJ Homepage)
Publication Date:
08/2003
Origin:
UCP
ApJ Keywords:
Infrared: Stars, Galaxy: Solar Neighborhood, Stars: Chemically Peculiar, Stars: Individual: Alphanumeric: 2MASS J05325346+8246465, Stars: Low-Mass, Brown Dwarfs, Stars: Subdwarfs
DOI:
10.1086/375813
Bibliographic Code:
2003ApJ...592.1186B

Abstract

We present the discovery of the first L-type subdwarf, 2MASS J05325346+8246465. This object exhibits enhanced collision-induced H2 absorption, resulting in blue near-infrared (NIR) colors (J-Ks=0.26+/-0.16). In addition, strong hydride bands in the red optical and NIR, weak TiO absorption, and an optical/J-band spectral morphology similar to the L7 DENIS 0205-1159AB imply a cool, metal-deficient atmosphere. We find that 2MASS 0532+8246 has both a high proper motion, μ=2.60"+/-0.15"yr-1, and a substantial radial velocity, vrad=-195+/-11 km s-1, and its probable proximity to the Sun (d=10-30 pc) is consistent with halo membership. Comparison to subsolar-metallicity evolutionary models strongly suggests that 2MASS 0532+8246 is substellar, with a mass of 0.077<~M<~0.085Msolar for ages 10-15 Gyr and metallicities Z=0.1-0.01Zsolar. The discovery of this object clearly indicates that star formation occurred below the hydrogen burning mass limit at early times, consistent with prior results indicating a flat or slightly rising mass function for the lowest mass stellar subdwarfs. Furthermore, 2MASS 0532+8246 serves as a prototype for a new spectral class of subdwarfs, additional examples of which could be found in NIR proper-motion surveys.
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