Characterizing Young Brown Dwarfs Using Low-Resolution Near-Infrared Spectra

By K. Allers, D. T. Jaffe, K. Luhman, Michael C. Liu, John C. Wilson, M. Skrutskie, M. Nelson, D. E. Peterson, John-David T. Smith, M. Cushing. 2006

173 citations recorded by the source corpus.

We present near-infrared (1.0-2.4 μm) spectra confirming the youth and cool temperatures of six brown dwarfs and low-mass stars with circumstellar disks toward the Chamaeleon II and Ophiuchus star-forming regions. The spectrum of one of our objects indicates a spectral type of ~L1, making it one of the latest spectral type young brown dwarfs identified to date. Comparing spectra of young brown dwarfs, field dwarfs, and giant stars, we define a 1.49-1.56 μm H2O index capable of determining spectral type to ±1 subtype, independent of gravity. We have also defined an index based on the 1.14 μm sodium feature that is sensitive to gravity, but only weakly dependent on spectral type. Our 1.14 μm Na index can be used to distinguish young cluster members (τ ≲ 5 Myr) from young field dwarfs, both of which may have the triangular H-band continuum shape that persists for at least tens of Myr. Using Teff values determined from the spectral types of our objects along with luminosities derived from near and mid-infrared photometry, we place our objects on the H-R diagram and overlay evolutionary models to estimate the masses and ages of our young sources. Three of our sources have inferred ages (τ ≃ 10-30 Myr) that are significantly older than the median stellar age of their parent clouds (1-3 Myr). For these three objects, we derive masses ~3 times greater than expected for 1-3 Myr old brown dwarfs with the bolometric luminosities of our sources. The large discrepancies in the inferred masses and ages determined using two separate, yet reasonable, methods emphasize the need for caution when deriving or exploiting brown dwarf mass and age estimates.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4e56fe099bd3eee339481d37fd6a5b77deb9193e

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Citations in the corpus

Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839–0446358 (2008, background): “…is now being devoted toward decrypting the spectral fingerprints of late-type dwarfs to determine masses, ages, metallicities and other fundamental parameters (e.g., Luhman & Rieke 1999; Gorlova et al. 2003; Burgasser, Burrows & Kirkpatrick 2007; Allers et al. 2007; Liu, Leggett, & Chiu 2007).”
The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, methodology): “The ability of the Spitzer Space Telescope (Werner et al. 2004) to collect sensitive, wide-field mid-IR images has made it possible to apply this technique on a much larger scale (Allers et al. 2007, Luhman et al. 2009b, 2006, Muench et al. 2007, Rebull et al. 2010).”
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).”
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): “…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, Gizis & Harvin 2006,…”
THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES (2008, background): “In particular, there is some evidence for longer lifetimes for in- 12 frared excesses around lower mass stars or brown dwarfs (Allers et al. 2007).”
Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich? (2008, background): “Reduced CIA H2 and/or increased condensate opacity are 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”
A REVISED AGE FOR UPPER SCORPIUS AND THE STAR FORMATION HISTORY AMONG THE F-TYPE MEMBERS OF THE SCORPIUS–CENTAURUS OB ASSOCIATION (2011, background): “However, followup spectroscopic studies (Allers et al. 2007; Close et al. 2007; Luhman et al. 2007) found higher masses.”