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

By A. Burgasser, J. D. Kirkpatrick, Adam Burrows, J. Liebert, I. Neill Reid, J. Gizis, M. R. McGovern, L. Prato, I. McLean. 2003

147 citations recorded by the source corpus.

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 ≲ 0.085 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3f780485a71ef0dddadb27678a006208b93ee0c4

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In Astronomy and Astrophysics

1. A. Burgasser
2. Michael C. Liu
3. J. D. Kirkpatrick
4. Kelle Cruz
5. K. Luhman
6. T. Dupuy
7. M. Marley
8. D. Schneider

In Instrumentation

1. A. Burgasser
2. Michael C. Liu
3. J. D. Kirkpatrick
4. Kelle Cruz
5. T. Dupuy
6. K. Luhman
7. M. Marley
8. I. Neill Reid

Citations in the corpus

• New spectral types L and T (2005, methodology): “…1 0 SOri 71 Zapatero Osorio et al. 2002 0 1 SOri 70 Scholz & Meusinger 2002 1 0 SSSPM J0829 − 1309 Liebert et al. 2003 1 0 2MASSI J0144353 − 071614 Burgasser et al. 2003c 0 1 2MASS J15031961 + 2525196 Scholz et al. 2003 0 1 Ind B Salim et al. 2003 1 0 LSR 0602 + 3910 Gizis et al. 2003 3 0…”
• Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field (2006, background): “Burgasser et al. (2003a) and Burgasser et al. (2006a) found evidence that condensate formation was inhibited in L subdwarf atmospheres due to the persistence of TiO molecular bands and Ti I and Ca I lines in their optical spectra.”
• Spitzer IRAC Photometry of M, L, and T Dwarfs (2006, background): “…SDS 0423 0414, 2MA 0746+2000,GJ337CD,SDS0926+5847,SDS1021 0304,Kelu-1, 2MA1225 2739, 2MA1534 2952, 2MA1553+1532, and 2MA 1728+3948 (Reid et al. 2001; Burgasser et al. 2003b, 2005a, 2005b, 2006b; Gizis et al. 2003; Bouy et al. 2004; Golimowski et al. 2004b; Vrba et al. 2004; Liu&Leggett 2005).”
• The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf Discoveries (2004, background): “In addition to these very low-luminosity sources, our search has identified one bona-fide ultracool halo subdwarf, the late-type sdL 2MASS 0532+8246 (Burgasser et al. 2003b), and now four candidate late-type subdwarfs requiring further verification.”
• Discovery of a Very Young Field L Dwarf, 2MASS J01415823–4633574 (2005, background): “3See the compilation at http://www.DwarfArchives.org. probably a low metallicity L dwarf member of the halo (Burgasser et al. 2003).”
• SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION (2009, background): “…al. (1999); (26) Siegler et al. (2007); (27) Burgasser et al. (2003b); (28) Burgasser (2007a); (29) Cruz et al. (2003); (30) Looper et al. (2007); (31) Burgasser et al. (2003d); (32) Burgasser et al. (2000a); (33) Reid et al. (2008); (34) Wilson et al. (2003); (35) Gizis (2002); (36) Burgasser et…”
• DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, background): “Each spectrum has been normalized to one at 8250 Å and overplotted on a suite of like-normalized LRIS spectra of primary M, L, and T optical spectral standards from Kirkpatrick et al. (1991), Kirkpatrick et al. (1999), and Burgasser et al. (2003).”
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity (2004, background): “Burgasser et al. (2003a) identified a late L dwarf (2MASS J05325346+8246465) whose extremely blue nearinfrared colors are similar to those of the mid T types.”
• Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich? (2008, background): “Several low metallicity L dwarfs have already been catalogued, the most relevant examples being the sdL4 2MASS J16262034+3925190 (hereafter 2MASS J1626+3925; Burgasser 2004) and the sdL7 2MASS J05325346+8246465 (hereafter 2MASS J0532+8246; Burgasser et al. 2003).”
• THE BROWN DWARF KINEMATICS PROJECT I. PROPER MOTIONS AND TANGENTIAL VELOCITIES FOR A LARGE SAMPLE OF LATE-TYPE M, L, AND T DWARFS (2008, background): “…objects (e.g. McGovern et al. 2004, Kirkpatrick et al. 2006, Allers et al. 2007, Cruz et al. 2007), 2) old, metal-poor ultracool subdwarfs (e.g. Burgasser et al. 2003a, Lépine et al. 2003, Gizis & Harvin 2006, Burgasser et al. 2007b), 3) unusually blue L dwarfs (hereafter UBLs; e.g. Cruz et…”
• The Spectra of T Dwarfs. II. Red Optical Data (2003, methodology): “Burgasser et al. (2003a) have estimated a J-band spectrophotometric distance of roughly 9 pc, implying vtan 60 km s 1, which suggests (but does not guarantee) membership in the Galactic thick disk or halo populations.”
• THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, background): “…24 = Burgasser et al. (2003d) 25 = Looper et al. (2007) 26 = Burgasser et al. (2004) 27 = Cruz et al. (2004) 28 = Burgasser et al. (2000b) 29 = Burgasser et al. (2003b) 30 = Cushing et al. (2009) 31 = Tinney et al. (2005) 32 = Burgasser et al. (2002a) 33 = Delfosse et al. (1997) 34 = Geballe…”