• DOI:10.1086/324078
• Corpus ID: 119455007

Toward Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis

@article{Geballe2001TowardSC,
  title={Toward Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis},
  author={Thomas R. Geballe and Gillian R. Knapp and Sandy K. Leggett and X. L. Fan and David A. Golimowski and Scott Anderson and Jonathan Brinkmann and Istv{\'a}n Csabai and James E. Gunn and Suzanne L. Hawley and Gregory S. Hennessy and Todd J. Henry and G. J. Hill and Robert B. Hindsley and Željko Ivezi{\'c} and Robert H. Lupton and A. McDaniel and Jeffrey A. Munn and Vijay K. Narayanan and Eric W. Peng and J. R. Pier and Constance M. Rockosi and Donald P. Schneider and J. Allyn Smith and Michael A. Strauss and Zlatan I. Tsvetanov and Alan K. Uomoto and Donald G. York and Wei Zheng},
  journal={The Astrophysical Journal},
  year={2001},
  volume={564},
  pages={466 - 481}
}

• T. Geballe, G. Knapp, +26 authors W. Zheng
• Published 28 August 2001
• Physics
• The Astrophysical Journal

We present 0.6-2.5 μm, R ≳ 400 spectra of 27 cool, low-luminosity stars and substellar objects. Based on these and previously published spectra, we develop a preliminary spectral classification system for L and T dwarfs. For late L and T types the classification system is based entirely on four spectral indices in the 1-2.5 μm interval. Two of these indices are derived from water absorption bands at 1.15 and 1.4 μm, the latter of which shows a smooth increase in depth through the L and T sequences and can be used to classify both spectral types. The other two indices make use of methane absorption features in the H and K bands, with the K-band index also applicable to mid-to-late L dwarfs. Continuum indices shortward of 1 μm used by previous authors to classify L dwarfs are found to be useful only through mid-L subclasses. We employ the 1.5 μm water index and the 2.2 μm methane index to complete the L classification through L9.5 and to link the new system with a modified version of the 2MASS "color-d" index. By correlating the depths of the methane and water absorption features, we establish a T spectral sequence from T0 to T8, based on all four indices, that is a smooth continuation of the L sequence. We reclassify two 2MASS L8 dwarfs as L9 and L9.5 and identify one SDSS object as L9. In the proposed system methane absorption appears in the K band approximately at L8, two subclasses earlier than its appearance in the H band. The L and T spectral classes are distinguished by the absence and presence, respectively, of H-band methane absorption.