A Spitzer Infrared Spectrograph Spectral Sequence of M, L, and T Dwarfs

By M. Cushing, T. Roellig, M. Marley, D. Saumon, S. Leggett, J. D. Kirkpatrick, John C. Wilson, G. Sloan, A. Mainzer, J. Cleve and 1 more. 2004

183 citations recorded by the source corpus.

We present a low-resolution (R ≡ λ/Δλ ≈ 90), 5.5-38 μm spectral sequence of a sample of M, L, and T dwarfs obtained with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. The spectra exhibit prominent absorption bands of H2O at 6.27 μm, CH4 at 7.65 μm, and NH3 at 10.5 μm and are relatively featureless at λ ≳ 15 μm. Three spectral indices that measure the strengths of these bands are presented; H2O absorption features are present throughout the MLT sequence, while the CH4 and NH3 bands first appear at roughly the L/T transition. Although the spectra are, in general, qualitatively well matched by synthetic spectra that include the formation of spatially homogeneous silicate and iron condensate clouds, the spectra of the mid-type L dwarfs show an unexpected flattening from roughly 9 to 11 μm. We hypothesize that this may be a result of a population of small silicate grains that are not predicted in the cloud models. The spectrum of the peculiar T6 dwarf 2MASS J0937+2931 is suppressed from 5.5 to 7.5 μm relative to typical T6 dwarfs and may be a consequence of its mildly metal-poor/high surface gravity atmosphere. Finally, we compute bolometric luminosities of a subsample of the M, L, and T dwarfs by combining the IRS spectra with previously published 0.6-4.1 μm spectra and find good agreement with the values of Golimowski et al., who use L′- and M′-band photometry to account for the flux emitted at λ > 2.5 μm.

Subfields: Aerospace Engineering, Analytical Chemistry, Mechanics of Materials

View Paper: https://www.semanticscholar.org/paper/33c3aa03f2a03b89236d211c7443a3513215a059

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Citations in the corpus

Discovery of Two T Dwarf Companions with the Spitzer Space Telescope (2006, background): “For instance, the bolometric luminosity for the T2 dwarf SDSS 1254-0122 from Cushing et al. (2006) implies BCK = 3.04.”
Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e (2020, background): “Retrieval analyses could be aided by longer wavelength data in the mid-IR, however, which could reveal the spectral features of cloud particles at ∼10 micron (Cushing et al. 2006).”
FURTHER DEFINING SPECTRAL TYPE “Y” AND EXPLORING THE LOW-MASS END OF THE FIELD BROWN DWARF MASS FUNCTION (2012, background): “…5 of Kirkpatrick (2008), the theoretical spectra of Burrows et al. (2003) indicate that absorption bands of NH3, which first appear in the mid-infrared (10.5 µm) near the L/T transition (Cushing et al. 2006), finally appear at the H and K bands starting near 800K and become prominent by 450K.”
DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, methodology): “The raw data were processed with the IRS pipeline (version S13) at the Spitzer Science Center and were further reduced as described in Cushing et al. (2006).”
THE DISCOVERY OF Y DWARFS USING DATA FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) (2011, background): “…by Burgasser 12 Although the fundamental band of NH3 has been detected in the spectra of warmer T dwarfs at 10.5 µm (e.g., Roellig et al. 2004; Cushing et al. 2006), the intrinsically weaker near-infrared bands require a higher NH3 abundance, and thus lower effective temperature, to become a…”
Transmission spectral properties of clouds for hot Jupiter exoplanets (2014, background): “Similar detections of broadband absorption features have been made in brown dwarf atmospheric spectra (Cushing et al. 2006, Burgasser et al. 2008), where absorption features observed in the mid infrared are attributed to clouds of small silicate grains in the photosphere of cloudy L dwarfs.”
MODEL ATMOSPHERES FOR MASSIVE GAS GIANTS WITH THICK CLOUDS: APPLICATION TO THE HR 8799 PLANETS AND PREDICTIONS FOR FUTURE DETECTIONS (2011, background): “Iron clouds have strong absorption in the visible, whereas silicates have strong spectral features at ∼10 µm and ∼20 µm which might be observable in high resolution spectra (Cushing et al. 2006; Helling et al. 2006; Henning 2010).”
SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION (2009, background): “…photospheres (Lodders 2002), as evident by their very red near-infrared colors, muted H2O absorption bands, weak TiO and VO bands (gaseous precursors to condensates) and presence of silicate grain features (e.g., Tsuji et al. 1996; Kirkpatrick et al. 1999; Knapp et al. 2004; Cushing et al. 2006).”
ATMOSPHERIC CHEMISTRY IN GIANT PLANETS, BROWN DWARFS, AND LOW-MASS DWARF STARS. III. IRON, MAGNESIUM, AND SILICON (2010, background): “…and fayalite (Fe2SiO4) are not expected in substellar atmospheres because nearly all Fe is removed from the gas phase by iron metal condensation at higher temperatures (e.g., Cushing et al. 2006; Lodders & Fegley 2006) Magnesium-silicate cloud formation is very effective at removing nearly all (>99”
NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES (2012, result): “When the opacity of these clouds is included in radiativeconvective equilibrium models of brown dwarf atmospheres, the resulting model spectra match those of observed L dwarfs (Cushing et al. 2006, 2008; Saumon & Marley 2008; Stephens et al. 2009).”
FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, methodology): “Though the flux in the range 14.5–17.26 μm constitutes 28% of the synthetic magnitude in W3, the relative lack of features at λ> 14.5 μm (Cushing et al. 2006) and our conservative estimate of uncertainty makes this a good approximation.”
THE EXTREMELY RED, YOUNG L DWARF PSO J318.5338−22.8603: A FREE-FLOATING PLANETARY-MASS ANALOG TO DIRECTLY IMAGED YOUNG GAS-GIANT PLANETS (2013, background): “5−22 and 2MASS J0355+11, respectively, very similar to field mid/late-L dwarfs (Golimowski et al. 2004; Cushing et al. 2006).”
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): “Cushing et al. (2006) suggested that models that also contain a population of smaller grains above the main cloud deck may do a better job of reproducing the 9 – 11 µm spectra of the redder L dwarfs.”
Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich? (2008, methodology): “The raw data were processed with the IRS pipeline (version S13) at the Spitzer Science Center and were further reduced as described in Cushing et al. (2006).”