Discovery of a Very Young Field L Dwarf, 2MASS J01415823–4633574

By J. D. Kirkpatrick, Travis S. Barman, A. Burgasser, M. R. McGovern, I. McLean, C. Tinney, P. Lowrance. 2005

188 citations recorded by the source corpus.

While following up L dwarf candidates selected photometrically from the Two Micron All Sky Survey, we uncovered an unusual object designated 2MASS J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium oxide but abnormally weak absorptions by titanium oxide, potassium, and sodium. Morphologically, such spectroscopic characteristics fall intermediate between old field early-L dwarfs [log(g) ≈ 5] and very late M giants [log(g) ≈ 0], leading us to favor low gravity as the explanation for the unique spectral signatures of this L dwarf. Such a low gravity can be explained only if this L dwarf is much lower in mass than a typical old field L dwarf of similar temperature and is still contracting to its final radius. These conditions imply a very young age. Further evidence of youth is found in the near-infrared spectrum, including a triangular-shaped H-band continuum, reminiscent of young brown dwarf candidates discovered in the Orion Nebula Cluster. Using the above information along with comparisons to brown dwarf atmospheric and interior models, our current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of 6-25MJ. Although the lack of a lithium detection (pseudo-equivalent width <1 Å) might appear to contradict other evidence of youth, we suggest that lithium becomes weaker at lower gravity like all other alkali lines and thus needs to be carefully considered before being used as a diagnostic of age or mass for objects in this regime. The location of 2MASS 0141-4633 on the sky coupled with a distance estimate of ~35 pc and the above age estimate suggests that this object may be a brown dwarf member of either the 30 Myr old Tucana/Horologium association or the ~12 Myr old β Pic moving group. Distance as determined through trigonometric parallax (underway) and a measure of the total space motion are needed to test this hypothesis.

Subfields: Astronomy and Astrophysics

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In Astronomy and Astrophysics

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

Citations in the corpus

• Discovery of 11 New T Dwarfs in the Two Micron All Sky Survey, Including a Possible L/T Transition Binary (2007, background): “By mid-type T, the spectral class is dominated by CH4, H2O, and collision induced absorption by H2 (CIA H2) in the near-infrared (Saumon et al. 1994; Borysow et al. 1997; Kirkpatrick et al. 2006).”
• THE FIRST HUNDRED BROWN DWARFS DISCOVERED BY THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) (2011, methodology): “The data were reduced and calibrated using standard IRAF routines as described in Kirkpatrick et al. (1999) and Kirkpatrick et al. (2006).”
• The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, methodology): “The classification of younger T dwarfs has not been explored since only a few candidates have been identified (Marsh, Kirkpatrick & Plavchan 2010; Zapatero Osorio et al. 2002).”
• A STUDY OF THE DIVERSE T DWARF POPULATION REVEALED BY WISE (2013, background): “Many of the known red L dwarfs are early-type and have accompanying optical spectra to facilitate classification and analysis (Looper et al. 2008; Kirkpatrick et al. 2006, 2010).”
• The Disk Population of the Chamaeleon I Star-forming Region (2008, background): “Finally, the spectral features that are sensitive to surface gravity in our data, such as the shape of the H- and K-band continua (Lucas et al. 2001; Luhman et al. 2004; Kirkpatrick et al. 2006), are inconsistent with field dwarfs and giants.”
• MEETING THE COOL NEIGHBORS. X. ULTRACOOL DWARFS FROM THE 2MASS ALL-SKY DATA RELEASE (2008, background): “This is generally interpreted as evidence for surface gravities that are lower than the typical values for field dwarfs of similar spectral types (Kirkpatrick et al., 2006).”
• THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION (2009, background): “…& Steeghs 2004; Luhman 2004a; Lyo et al. 2004; Song et al. 2004; Zuckerman & Song 2004; Mamajek 2005; Scholz et al. 2005; Looper et al. 2007; Luhman et al. 2008a; Kastner et al. 2008) and young late-type dwarfs in the solar neighborhood (Kirkpatrick et al. 2006, 2008; Cruz et al. 2007, 2009).”
• THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, background): “Kirkpatrick et al. (2006) and Cruz et al. (2009) have suggested that a number of the lowsurface gravity dwarfs are candidate members of nearby moving groups such as β Pictoris, Tucana-Horlogium, and AB Doradus, implying ages roughly spanning 10- 50 Myr (e.g. Rice et al. 2010) .”
• Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field (2006, methodology): “In particular, we have used enhanced VO bands (7330–7530, 7850–8000 Å), less-broad K I doublet (7665, 7699 Å), and weaker Na I doublet (8183, 8195 Å) as diagnostics (Mart́ın et al. 1996; Gizis et al. 1999; Gorlova et al. 2003; McGovern et al. 2004; Kirkpatrick et al. 2006a).”
• AN INFRARED/X-RAY SURVEY FOR NEW MEMBERS OF THE TAURUS STAR-FORMING REGION (2009, methodology): “We classified this object through a comparison to standard L dwarfs (Kirkpatrick et al. 1999) and young L dwarfs in the field (τ ∼ 10-100 Myr, Kirkpatrick et al. 2006; Cruz et al. 2009), arriving at a spectral type of L0 (see Figure 2).”
• CLOUDS AND CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HR8799b (2011, background): “The shape of the H band is often used as a gravity indicator in L-type brown dwarfs, where low gravity objects have distinct triangular spectra (Lucas et al. 2001; Kirkpatrick et al. 2006) compared to the more rounded spectra of older, higher gravity, field brown dwarfs.”
• 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): “Currently defined subgroups of late-type M, L and T dwarfs include 1) low surface-gravity, very low-mass 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,…”
• THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, background): “…are still important aspects of brown dwarf evolution that would benefit from a larger set of distance measurements: young field brown dwarfs (e.g., Kirkpatrick et al. 2006; Allers et al. 2009; Cruz et al. 2009), the coldest brown dwarfs (.500 K, e.g., Lucas et al. 2010; Cushing et al. 2011), and…”
• A NEAR-INFRARED SPECTROSCOPIC STUDY OF YOUNG FIELD ULTRACOOL DWARFS (2013, background): “Only a handful of young field brown dwarfs have been studied in detail in the near-infrared (e.g. Allers et al. 2010; Kirkpatrick et al. 2006).”
• ExoMol line lists – XVIII. The high-temperature spectrum of VO (2016, background): “VO is one of the dominant species in the spectra of young hot brown dwarfs (McGovern et al. 2004; Kirkpatrick et al. 2006; Peterson et al. 2008).”
• Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich? (2008, background): “…likely responsible for the triangular-shaped H-band spectra characteristic of low-gravity, late-type M and earlytype L dwarfs seen both in young clusters (e.g., Orion: Lucas et al. 2001; Cha II, Rho Oph: Allers et al. 2007) and associations (e.g., Kirkpatrick et al. 2006; TWA: Looper et al. 2007b).”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, background): “Since it is well documented that the colors of ultracool dwarfs are sensitive to age (Kirkpatrick et al. 2006, 2008; Cruz et al. 2009; Faherty et al. 2009; Allers et al. 2010; Bihain et al. 2010; Faherty et al. 2012; Schmidt et al. 2010), we derived one polynomial for the field age objects (MFLD)…”
• DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, background): “2MASS J04062677−3812102: The optical spectrum of this object (Figure 12) is a good match to that of 2MASS J0141−4633, giving 2MASS J0406−3812 an optical type of L0γ.”
• The Stellar Population of the Chamaeleon I Star-forming Region (2007, background): “Individual brown dwarfs that are not part of IMF measurements have also been found near masses of ∼ 0.01 M⊙ (Kirkpatrick et al. 2006; Allers et al. 2006, 2007).”