The First Substellar Subdwarf? Discovery of a Metal-poor L Dwarf with Halo Kinematics

August 2003 • 2003ApJ...592.1186B

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.

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-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, v_rad=-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<~0.085M_solar for ages 10-15 Gyr and metallicities Z=0.1-0.01Z_solar. 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.

Links

• PREPRINT http://arxiv.org/abs/astro-ph/0304174
• SPIRES http://inspirehep.net/search?p=find+j+ASJOA,592,1186
• ELECTR https://doi.org/10.1086%2F375813
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2003ApJ...592.1186B
• PDF https://stacks.iop.org/0004-637X/592/1186/pdf
• DATA https://irsa.ipac.caltech.edu/bibdata/2003/B/2003ApJ...592.1186B.html
• SPIRES http://inspirehep.net/search?p=find+eprint+astro-ph/0304174