宽视场红外巡天探测器发现的五颗晚型T矮星的FIRE光谱
FIRE Spectroscopy of Five Late-type T Dwarfs Discovered with the Wide-field Infrared Survey Explorer
摘要：
我们介绍了宽视场红外巡天探测器（WISE）发现的五颗晚型T矮星。低分辨率近红外光谱获得的麦哲伦折叠端口红梯队（FIRE）显示强烈的水和甲烷吸收在所有五个来源，光谱指数和比较光谱模板表明分类范围从T5.5到T8.5：。最新类型的源WISE J1812+2721的光谱与T8.5伴星狼940 B的光谱非常匹配。基于WISE的分光光度距离估计将这些T矮星放置在距离太阳12-13 pc处，假设它们是单一的。光谱数据与Saumon & Marley大气模型的初步拟合表明，有效温度范围从600 K到930 K，多云和无云大气，以及广泛的年龄和质量。特别是，两个来源显示了低表面重力和多云大气的证据，初步支持了其他年轻棕矮星和系外行星的趋势。相比之下，高自行T矮星WISE J2018-7423表现出抑制的K带峰和蓝色分光光度J-K颜色，表明是一颗古老的大质量棕矮星;然而，它缺乏在贫金属对应物中看到的加宽的Y带峰。这些结果说明了WISE将发现的低温褐矮星的广泛多样性。
英文摘要：
We present the discovery of five late-type T dwarfs identified with the Wide-field Infrared Survey Explorer (WISE). Low-resolution near-infrared spectroscopy obtained with the Magellan Folded-port InfraRed Echellette (FIRE) reveal strong water and methane absorption in all five sources, and spectral indices and comparison to spectral templates indicate classifications ranging from T5.5 to T8.5:. The spectrum of the latest-type source, WISE J1812+2721, is an excellent match to that of the T8.5 companion brown dwarf Wolf 940B. WISE-based spectrophotometric distance estimates place these T dwarfs at 12-13 pc from the Sun, assuming they are single. Preliminary fits of the spectral data to the atmosphere models of Saumon & Marley indicate effective temperatures ranging from 600 K to 930 K, both cloudy and cloud-free atmospheres, and a broad range of ages and masses. In particular, two sources show evidence of both low surface gravity and cloudy atmospheres, tentatively supporting a trend noted in other young brown dwarfs and exoplanets. In contrast, the high proper motion T dwarf WISE J2018-7423 exhibits a suppressed K-band peak and blue spectrophotometric J-K colors indicative of an old, massive brown dwarf; however, it lacks the broadened Y-band peak seen in metal-poor counterparts. These results illustrate the broad diversity of low-temperature brown dwarfs that will be uncovered with WISE.
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