TY - JOUR
T1 - The first substellar subdwarf? Discovery of a metal-poor L dwarf with halo kinematics
AU - Burgasser, Adam J.
AU - Kirkpatrick, J. Davy
AU - Burrows, Adam S.
AU - Liebert, James
AU - Reid, I. Neill
AU - Gizis, John E.
AU - Mcgovern, Mark R.
AU - Prato, L.
AU - McLean, Ian S.
N1 - Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2003/8/1
Y1 - 2003/8/1
N2 - 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.
AB - 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.
KW - Infrared: stars
KW - Solar neighborhood
KW - Stars: chemically peculiar
KW - Stars: low-mass, brown dwarfs
KW - Subdwarfs
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U2 - 10.1086/375813
DO - 10.1086/375813
M3 - Article
AN - SCOPUS:0041832087
VL - 592
SP - 1186
EP - 1192
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2 I
ER -