NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES
NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES
复制标题
T 和 Y 矮星大气中被忽视的云
DOI：
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S. Leggett
中科院分区：
文献类型：
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作者：
C. Morley;J. Fortney;M. Marley;C. Visscher;D. Saumon;S. Leggett
当褐矮星冷却时，各种各样的物质在它们的大气中凝结，形成云。铁云和硅酸盐云塑造了L矮星的出射光谱，但这些云在L/T转变时消散。在温度较低的T矮大气中，预计会形成各种其他的冷凝物。这些云包括Cr、MnS、Na 2S、ZnS和KCl，但这些光学上较薄的云的不透明性在以前的大气模型中还没有被包括在内。在这里，我们研究它们对模型T和Y矮大气的影响。云的结构和不透明度的计算使用阿克曼和马利云模式，这是耦合到大气模式，以产生大气压力-温度廓线在辐射对流平衡。我们生成一套模型Teff = 400和1300 K之间，log g = 4.0和5.5，和冷凝物沉降效率从fsed = 2至5。将模型光谱与两颗红T矮星Ross 458 C和UGPS 0722-05进行了比较;发现包含云的模型与观测光谱的匹配明显优于无云模型。冷大气中硫化物云的出现，特别是Na 2S，可能是这些天体“多云”光谱的一个更自然的解释，而不是在L-to-T转变时减弱的硅酸盐云的重新出现。我们发现，硫化物云提供了一种机制，以配合观察到的T矮星的近红外和中红外颜色。我们的研究结果表明，包括在T矮大气中的冷凝物的不透明度是必要的，以准确地确定许多观测对象的物理特性。
As brown dwarfs cool, a variety of species condense in their atmospheres, forming clouds. Iron and silicate clouds shape the emergent spectra of L dwarfs, but these clouds dissipate at the L/T transition. A variety of other condensates are expected to form in cooler T dwarf atmospheres. These include Cr, MnS, Na2S, ZnS, and KCl, but the opacity of these optically thinner clouds has not been included in previous atmosphere models. Here, we examine their effect on model T and Y dwarf atmospheres. The cloud structures and opacities are calculated using the Ackerman & Marley cloud model, which is coupled to an atmosphere model to produce atmospheric pressure–temperature profiles in radiative–convective equilibrium. We generate a suite of models between Teff = 400 and 1300 K, log g = 4.0 and 5.5, and condensate sedimentation efficiencies from fsed = 2 to 5. Model spectra are compared to two red T dwarfs, Ross 458C and UGPS 0722–05; models that include clouds are found to match observed spectra significantly better than cloudless models. The emergence of sulfide clouds in cool atmospheres, particularly Na2S, may be a more natural explanation for the “cloudy” spectra of these objects, rather than the reemergence of silicate clouds that wane at the L-to-T transition. We find that sulfide clouds provide a mechanism to match the near- and mid-infrared colors of observed T dwarfs. Our results indicate that including the opacity of condensates in T dwarf atmospheres is necessary to accurately determine the physical characteristics of many of the observed objects.
褐矮星和太阳系外行星中的尘埃 II 宇宙演化丰度的云形成
影响因子：
6.5
作者：
Helling;Hauschildt
通讯作者：
Hauschildt