A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs

By A. Burgasser, T. Geballe, S. Leggett, J. D. Kirkpatrick, D. Golimowski. 2005

413 citations recorded by the source corpus.

A revised near-infrared classification scheme for T dwarfs is presented, based on and superseding prior schemes developed by Burgasser and coworkers and Geballe and coworkers, and defined following the precepts of the MK process. Drawing from two large spectroscopic libraries of T dwarfs identified largely in the Sloan Digital Sky Survey and the Two Micron All Sky Survey, nine primary spectral standards and five alternate standards spanning spectral types T0-T8 are identified that match criteria of spectral character, brightness, absence of a resolved companion, and accessibility from both the Northern and Southern Hemispheres. The classification of T dwarfs is formally made by the direct comparison of near-infrared spectral data of equivalent resolution to the spectra of these standards. Alternately, we have redefined five key spectral indices measuring the strengths of the major H2O and CH4 bands in the 1-2.5 μm region that may be used as a proxy to direct spectral comparison. Two methods of determining T spectral type using these indices are outlined and yield equivalent results. These classifications are also equivalent to those from prior schemes, implying that no revision of existing spectral type trends is required. The one-dimensional scheme presented here provides a first step toward the observational characterization of the lowest luminosity brown dwarfs currently known. Future extensions to incorporate spectral variations arising from differences in photospheric dust content, gravity, and metallicity are briefly discussed. A compendium of all currently known T dwarfs with updated classifications is presented.

Subfields: Astronomy and Astrophysics, Instrumentation, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/aad0cc585d27b35d307908b166320b524ee2c7c8

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In Astronomy and Astrophysics

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

In Instrumentation

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

In Spectroscopy

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

Citations in the corpus

• Discovery of Two T Dwarf Companions with the Spitzer Space Telescope (2006, methodology): “In contrast, the spectral modeling of late T dwarfs by Burgasser et al. (2006b) found that temperature should increase rather than decrease with lower gravity at a given spectral type.”
• HST SPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS (2013, background): “Based on JHK light curves and a fit to the spectrum by (Burgasser et al. 2006) these authors argue that cloud thickness variations are likely responsible for the photometric variations seen in 2M2139.”
• Individual Dynamical Masses of Ultracool Dwarfs (2017, result): “— Burg03b = Burgasser et al. (2003b); Burg06b = Burgasser et al. (2006b); Burg11 = Burgasser et al. (2011); Chiu06 = Chiu et al. (2006); Clos03 = Close et al. (2003); Cutr03 = Cutri et al. (2003); Dupu09a = Dupuy et al. (2009a); Dupu09b = Dupuy et al. (2009b); Dupu09c = Dupuy et al. (2009c); Dupu10…”
• THE INFRARED TELESCOPE FACILITY (IRTF) SPECTRAL LIBRARY: COOL STARS (2009, background): “The sample of 13 L and two T dwarfs from Cushing et al. (2005), and the eight T dwarf spectral standards from Burgasser et al. (2006) are also included in these figures and table.”
• DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, background): “Surprisingly, however, a set of near-infrared M and L dwarf anchors has never been established although those for T dwarfs have been (Burgasser et al. 2006).”
• LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES (2012, methodology): “In the SpeX Prism Library there are two low resolution NIR spectra (R∼120) for 2M2139 , obtained in 2003 and 2004 by Burgasser et al. (2006).”
• A Spitzer Infrared Spectrograph Spectral Sequence of M, L, and T Dwarfs (2004, methodology): “…L and T dwarfs can be found at http://DwarfArchives.org and http://www.jach.hawaii.edu/~skl/LTdata.html are listed in Table 1, we hereafter use optical types for the M and L dwarfs (Kirkpatrick et al. 1991, 1999) and infrared types for the T dwarfs (Burgasser et al. 2006) unless otherwise noted.”
• A T8.5 BROWN DWARF MEMBER OF THE ξ URSAE MAJORIS SYSTEM (2012, methodology): “We derive a more precise spectral type using the spectral classification schemes of Burgasser et al. (2006) and the extension to this system by Cushing et al. (2011) whereby UGPS J072227.”
• MID-INFRARED PHOTOMETRY OF COLD BROWN DWARFS: DIVERSITY IN AGE, MASS, AND METALLICITY (2010, methodology): “The primary sample for this paper consists of T dwarfs with spectral types T7 and later, as defined by the Burgasser et al. (2006b) scheme.”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, neutral): “(1) Knapp et al. (2004), (2) Burgasser et al. (2006a), (3) Kirkpatrick et al. (2010), (4) Cruz et al. (2009), (5) Goldman et al. (1999), (6) Kirkpatrick et al. (2001a), (7) Cruz & Reid (2002), (8) Kirkpatrick et al. (1995), (9) Cruz et al. (2007), (10) Faherty et al. (2009), (11) Schneider et al.…”
• MEETING THE COOL NEIGHBORS. X. ULTRACOOL DWARFS FROM THE 2MASS ALL-SKY DATA RELEASE (2008, methodology): “Moreover, Burgasser et al. (2006) have obtained low resolution, near-infrared spectra that indicate the presence of methane absorption.”
• The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, background): “For field T dwarfs, the primary classification scheme is based on near-IR H2O and C2H4 bands (Burgasser et al. 2006).”
• THE DISCOVERY OF Y DWARFS USING DATA FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) (2011, methodology): “The emergent spectra of brown dwarfs are so distinct from that of late-type M dwarfs that the creation of two new spectral classes, L and T (Kirkpatrick et al. 1999; Burgasser et al. 2006), was required in order to properly classify them11.”
• Discovery of 11 New T Dwarfs in the Two Micron All Sky Survey, Including a Possible L/T Transition Binary (2007, methodology): “We augmented the SpeX spectra from Burgasser et al. (2006a) with new spectra for SDSS J120747.”
• THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, methodology): “…(8) Bonnefoy et al. (2010); (9) Bonnefoy et al. (2011); (10) Bonnefoy et al. (2014a); (11) Bonnefoy et al. (2014b); (12) Bouvier et al. (2008); (13) Burgasser et al. (2006); (14) Burgasser & McElwain (2006); (15) Burgasser et al. (2011); (16) Chauvin et al. (2004); (17) Chauvin et al. (2005b);…”
• THE 0.8–14.5 μm SPECTRA OF MID-L TO MID-T DWARFS: DIAGNOSTICS OF EFFECTIVE TEMPERATURE, GRAIN SEDIMENTATION, GAS TRANSPORT, AND SURFACE GRAVITY (2009, methodology): “This brightening is a real effect and not due to variations in other parameters as verified by several studies of binary systems (Gizis et al. 2003, Cruz et al. 2004, Burgasser et al. 2006b, Liu et al. 2006, Looper et al. 2008).”
• Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey (2006, methodology): “If both schemes indicated an early T type, then the unified T classification of Burgasser et al. (2006a) was used.”