Planck-cmb-allsky

2MASS J06164006-6407194: The First Outer Halo L Subdwarf

May 2009 • 2009ApJ...696..986C

Authors • Cushing, Michael C. • Looper, Dagny • Burgasser, Adam J. • Kirkpatrick, J. Davy • Faherty, Jacqueline • Cruz, Kelle L. • Sweet, Anne • Sanderson, Robyn E.

Abstract • We present the serendipitous discovery of an L subdwarf in the Two Micron All Sky Survey (2MASS) J06164006-6407194, in a search of the 2MASS for T dwarfs. Its spectrum exhibits features indicative of both a cool and metal poor atmosphere including a heavily pressure-broadened K I resonant doublet, Cs I and Rb I lines, molecular bands of CaH, TiO, CrH, FeH, and H2O, and enhanced collision induced absorption of H2. We assign 2MASS J0616-6407 a spectral type of sdL5 based on a comparison of its red optical spectrum to that of near solar-metallicity L dwarfs. Its high proper motion (μ = 1farcs405 ± 0.008 yr-1), large radial velocity (V rad = 454 ± 15 km s-1), estimated u, v, w velocities (94, -573, 125) km s-1 and Galactic orbit with an apogalacticon at ~29 kpc are indicative of membership in the outer halo making 2MASS J0616-6407 the first ultracool member of this population.

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Davy Kirkpatrick

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