Kirkpatrick, J. Davy (2005) New spectral types L and T. Annual Review of Astronomy and Astrophysics, 43 . pp. 195-245. ISSN 0066-4146 http://resolver.caltech.edu/CaltechAUTHORS:KIRaraa05
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The establishment of new spectral classes cooler than type M has had a brief, yet already rich, history. Prototypes of the new "L dwarf" and "T dwarf" classes were first found in the late 1980s to mid-1990s, with a flood of new discoveries occurring in the late 1990s with the advent of deep, large-area, digital sky surveys. Over four hundred and fifty L and T dwarfs are now cataloged. This review concentrates on the spectroscopic properties of these objects, beginning with the establishment of classification schemes rooted in the MK Process. The resulting grid of spectral types is then used as a tool to ferret out the underlying physics. The temperature ranges covered by these spectral types, the complex chemical processes responsible for the shape of their emergent spectra, their nature as either true stars or brown dwarfs, and their number density in the Galaxy are discussed. Two promising avenues for future research are also explored: the extension of the classification system to three dimensions to account for gravity- and metallicity-dependent features, and the capability of newer large-area surveys to uncover brown dwarfs cooler than those now recognized.
|Additional Information:||"Reprinted, with permission, from the Annual Review of Astronomy & Astrophysics, Volume 43 copyright 2005 by Annual Reviews, www.annualreviews.org" First published online as a Review in Advance on May 19, 2005. The author would like to thank George Helou (IPAC) for providing partial salary support during the writing of this manuscript. The author is also indebted to Peter Allen, Adam Burgasser, Kelle Cruz, Michael Cushing, Jim Emerson, Chris Gelino, Sandy Leggett, Jim Liebert, Michael Liu, Mark McGovern, Ian McLean, Tadashi Nakajima, Keith Noll, Ben Oppenheimer, Neill Reid, Tom Roellig, and Didier Saumon for valuable discussions, use of data sets, and/or access to papers prior to their publication. The construction of Table 1, Table 3, and Figures 8–9 relied heavily on NASA’s Astrophysics Data System (ADS) Bibliographic Services and the NASA/IPAC Infrared Science Archive (IRSA). The latter is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Almost all of the spectra illustrated in Figures 1–5 were obtained atop Mauna Kea on the Big Island of Hawaii. The author wishes to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. He and his colleagues consider themselves most fortunate to have had the opportunity to conduct observations from this mountain.|
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|Deposited On:||31 Oct 2005|
|Last Modified:||26 Dec 2012 08:41|
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