POSTER PAPER 2.08
Infrared Classification of L and T Dwarfs
T. R. Geballe, G. R. Knapp, S. K. Leggett, X. Fan, and D. A. Golimowski
Institute: Gemini Observatory, Hawaii
Institute: Princeton University Observatory
Institute: Joint Astronomy Centre, Hawaii
Institute: Institute for Advanced Study, Princeton
Institute: The Johns Hopkins University, Baltimore
Contact Email: tgeballe@gemini.edu
Abstract:
We use new and published medium resolution 0.6--2.5 micrometer spectra of L
and T dwarfs to develop a unified classification system for both of these
new spectral classes. Two indices of the system at 1.2 micrometers and
1.5 micrometers are based on nearby absorption bands of water vapor and two are
associated with methane bands near 1.6 micrometers and 2.2 micrometers. The
1.5 micrometer index is monotonic through the L and T sequences, and forms
the backbone of the system; the indices for the other bands provide
extensive, but only partial, coverage. We correlate the 1.5 micrometer index
with continuum indices shortward of 1 micrometer devised by others for
classifying L dwarfs, in order to obtain a tight link between optical and
infrared classifications. Our proposed system defines ten spectral
subclasses for L (L0--L9) and nine for T (T0--T8). The boundary between L
and T is defined to be the onset of absorption by methane in the H band.
Methane absorption in the K band near 2.2 micrometers is found to begin
approximately at L8.
Index Keywords: Classification; L Dwarfs; T Dwarfs; Brown Dwarfs
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Manuscript submitted: 2001-Sep-05
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.