A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs
A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs
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DOI：
10.1086/498563
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发表时间：
2005-10
期刊：
影响因子：
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通讯作者：
A. Burgasser;T. Geballe;S. Leggett;J. Kirkpatrick;D. Golimowski
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文献类型：
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作者：
A. Burgasser;T. Geballe;S. Leggett;J. Kirkpatrick;D. Golimowski
本文提出了一个修正的T矮星近红外分类方案，它是基于并取代Burgasser及其同事和Geballe及其同事提出的先前方案，并根据MK过程的规则定义的。从两个大型光谱库的T矮星主要是在斯隆数字巡天和两微米全天巡天确定，九个主要的光谱标准和五个替代标准跨越光谱类型T0-T8的确定，匹配标准的光谱特征，亮度，没有解决的同伴，并从北方和南半球的可访问性。T型矮星的分类是通过直接比较等分辨率的近红外光谱数据和这些标准的光谱而正式作出的。或者，我们重新定义了五个关键光谱指数，用于测量1-2.5 μm区域中主要H2O和CH 4谱带的强度，可用作直接光谱比较的代理。两种方法确定T谱型使用这些指标的概述和产生等效的结果。这些分类也相当于那些从以前的计划，这意味着没有修改现有的光谱类型的趋势是必要的。这里提出的一维方案为目前已知的最低光度棕矮星的观测特征提供了第一步。未来的扩展，将光谱变化所产生的光球尘埃含量，重力和金属丰度的差异进行了简要讨论。目前已知的所有T型矮星与更新的分类纲要。
A revised near-infrared classification scheme for T dwarfs is presented, based on and superseding prior schemes developed by Burgasser and coworkers and Geballe and coworkers, and defined following the precepts of the MK process. Drawing from two large spectroscopic libraries of T dwarfs identified largely in the Sloan Digital Sky Survey and the Two Micron All Sky Survey, nine primary spectral standards and five alternate standards spanning spectral types T0-T8 are identified that match criteria of spectral character, brightness, absence of a resolved companion, and accessibility from both the Northern and Southern Hemispheres. The classification of T dwarfs is formally made by the direct comparison of near-infrared spectral data of equivalent resolution to the spectra of these standards. Alternately, we have redefined five key spectral indices measuring the strengths of the major H2O and CH4 bands in the 1-2.5 μm region that may be used as a proxy to direct spectral comparison. Two methods of determining T spectral type using these indices are outlined and yield equivalent results. These classifications are also equivalent to those from prior schemes, implying that no revision of existing spectral type trends is required. The one-dimensional scheme presented here provides a first step toward the observational characterization of the lowest luminosity brown dwarfs currently known. Future extensions to incorporate spectral variations arising from differences in photospheric dust content, gravity, and metallicity are briefly discussed. A compendium of all currently known T dwarfs with updated classifications is presented.