The first substellar subdwarf? Discovery of a metal-poor L dwarf with halo kinematics

Adam J. Burgasser, J. Davy Kirkpatrick, Adam S. Burrows, James Liebert, I. Neill Reid, John E. Gizis, Mark R. Mcgovern, L. Prato, Ian S. McLean

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We present the discovery of the first L-type subdwarf, 2MASS J05325346+8246465. This object exhibits enhanced collision-induced H 2 absorption, resulting in blue near-infrared (NIR) colors (J-K s = 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 ≲0.085 M for ages 10-15 Gyr and metallicities Z = 0.1-0.01 Z . 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.

Original languageEnglish (US)
Pages (from-to)1186-1192
Number of pages7
JournalAstrophysical Journal
Issue number2 I
StatePublished - Aug 1 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Infrared: stars
  • Solar neighborhood
  • Stars: chemically peculiar
  • Stars: low-mass, brown dwarfs
  • Subdwarfs


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