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Title:
An Infrared Spectroscopic Sequence of M, L, and T Dwarfs
Authors:
Cushing, Michael C.; Rayner, John T.; Vacca, William D.
Affiliation:
AA(SETI Institute, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035; ), AB(Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822; ), AC(SOFIA-USRA, NASA Ames Research Center, MS 144-2, Moffett Field, CA 94035; )
Publication:
The Astrophysical Journal, Volume 623, Issue 2, pp. 1115-1140. (ApJ Homepage)
Publication Date:
04/2005
Origin:
UCP
ApJ Keywords:
Infrared: Stars, Stars: Fundamental Parameters, Stars: Individual: Alphanumeric: 2MASS J2224381-0158521, Stars: Late-Type, Stars: Low-Mass, Brown Dwarfs
DOI:
10.1086/428040
Bibliographic Code:
2005ApJ...623.1115C

Abstract

We present a 0.6-4.1 μm spectroscopic sequence of M, L, and T dwarfs. The spectra have R≡λ/Δλ~2000 from 0.9 to 2.4 μm and R=2500-200 from 2.9 to 4.1 μm. These new data nearly double the number of L and T dwarfs that have reported L-band spectra. The near-infrared spectra are combined with previously published red-optical spectra to extend the wavelength coverage to ~0.6 μm. Prominent atomic and molecular absorption features are identified including neutral lines of Al, Fe, Mg, Ca, Ti, Na, and K and 19 new weak CH4 absorption features in the H-band spectra of mid- to late-type T dwarfs. In addition, we detect for the first time the 0-0 band of the A 4Π-X 4Σ- transition of VO at ~1.06 μm in the spectra of L dwarfs and the P- and R-branches of the ν3 band of CH4 in the spectrum of a T dwarf. The equivalent widths of the refractory atomic features all decrease with increasing spectral type and are absent by a spectral type of ~L0, except for the 1.189 μm Fe I line, which persists to at least ~L3. We compute the bolometric luminosities of the dwarfs in our sample with measured parallaxes and find good agreement with previously published results that use L'-band photometry to account for the flux emitted from 2.5 to 3.6 μm. Finally, 2MASS J2224381-0158521 (L4.5) has an anomalously red spectrum and the strongest Δν=+2 CO bands in our sample. This may be indicative of unusually thick condensate clouds and/or low surface gravity.

Based in part on data collected at Subaru telescope, which is operated by the National Astronomical Observatory of Japan.


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