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arXiv 0912.2350astro-ph.EP
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三维热木星模型大气的透射谱

Transmission Spectra of Three-Dimensional Hot Jupiter Model Atmospheres

J. J. Fortney, M. Shabram, A. P. Showman, Y. Lian, R. S. Freedman, M. S. Marley, N. K. Lewis

摘要:

我们计算模型的行星HD 209458 b,HD 189733 b,和一般的热彗星的透射光谱。我们研究了温度,表面重力和金属丰度的一般行星的影响,作为一般理解透射光谱的指导。我们发现,在4.4和15微米的二氧化碳吸收是突出的高金属丰度,是一个明确的金属丰度指标。对于HD 209458b和HD 189733b,我们计算了一维和三维模型大气的光谱,并研究了它们之间的差异。差异通常很小,但如果大气温度接近重要的化学丰度边界,差异可能很大。三维大气的计算,以及它们与数据的比较,作为对这些动力学模型的约束,补充了二次日食和光变曲线数据集。对于HD 209458b,即使TiO和VO气体在白天丰富,它们的丰度在较冷的行星边缘会大大减少。然而,考虑到预测的边缘温度和TiO丰度,该模型的光学不透明度太高。对于HD 189733b,我们发现与一些红外数据集很好地匹配,并限制了假设的霾层的高度。对于这颗行星来说,领先和落后半球的透射光谱之间可能存在很大的差异,这是碳化学的一个很好的探针。在热化学平衡中,较冷的前半球以甲烷为主,较热的后半球以CO为主,但由于垂直混合,这些差异可能会被非平衡化学消除。JWST有可能限制这颗行星的碳化学及其空间变化。

英文摘要:

We compute models of the transmission spectra of planets HD 209458b, HD 189733b, and generic hot Jupiters. We examine the effects of temperature, surface gravity, and metallicity for the generic planets as a guide to understanding transmission spectra in general. We find that carbon dioxide absorption at 4.4 and 15 microns is prominent at high metallicity, and is a clear metallicity indicator. For HD 209458b and HD 189733b, we compute spectra for both one-dimensional and three-dimensional model atmospheres and examine the differences between them. The differences are usually small, but can be large if atmospheric temperatures are near important chemical abundance boundaries. The calculations for the 3D atmospheres, and their comparison with data, serve as constraints on these dynamical models that complement the secondary eclipse and light curve data sets. For HD 209458b, even if TiO and VO gases are abundant on the day side, their abundances can be considerably reduced on the cooler planetary limb. However, given the predicted limb temperatures and TiO abundances, the model's optical opacity is too high. For HD 189733b we find a good match with some infrared data sets and constrain the altitude of a postulated haze layer. For this planet, substantial differences can exist between the transmission spectra of the leading and trailing hemispheres, which is an excellent probe of carbon chemistry. In thermochemical equilibrium, the cooler leading hemisphere is methane-dominated, and the hotter trailing hemisphere is CO-dominated, but these differences may be eliminated by non-equilibrium chemistry due to vertical mixing. It may be possible to constrain the carbon chemistry of this planet, and its spatial variation, with JWST.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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