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arXiv 1602.03088astro-ph.EPastro-ph.SR
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热彗星云成分的转变

Transitions in the cloud composition of hot Jupiters

Vivien Parmentier, Jonathan J. Fortney, Adam P. Showman, Caroline V. Morley, Mark S. Marley

备注：
Accepted for publication in ApJ. Revised version include effect of metallicity, CaTiO3 clouds, and models with an updated Al2O3 condensation curve. Conclusions are unchanged
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摘要：

在很大的平衡温度范围内，云塑造了热木星大气的透射光谱，但它们的组成仍然未知。最近的观测表明，一些热彗星的开普勒光变曲线是不对称的：对于最热的行星，光变曲线在二次食之前达到峰值，而对于比$\sim1900\rm\,K$冷的行星，光变曲线在二次食之后达到峰值。我们使用三维全球环流模式的热结构，以确定预期的云分布和热彗星的开普勒光变曲线。我们表明，从一个光学光变曲线为主的热发射为主的散射（反射）自然解释了观察到的趋势从负到正的偏移。对于冷行星，开普勒光变曲线的不对称性是云组成的一个迹象，因为每种云只能在一个狭窄的有效温度范围内产生偏移。通过比较我们的模型和观测结果，我们表明，云组成的热彗星可能随平衡温度。我们认为硅酸盐和硫化锰云之间的过渡发生在$1600\rm\,K$附近的温度，类似于棕矮星的L/T转变。光球层下方的云物种的冷捕获自然会产生这样的转变，并预测其他冷凝物，包括TiO类似的转变。我们预测，大多数炎热的热带气旋应该有多云的夜面，部分云量应该是常见的边缘和白天的热点应该经常是无云的。

英文摘要：

Over a large range of equilibrium temperatures, clouds shape the transmission spectrum of hot Jupiter atmospheres, yet their composition remains unknown. Recent observations show that the Kepler lightcurves of some hot Jupiters are asymmetric: for the hottest planets, the lightcurve peaks before secondary eclipse, whereas for planets cooler than $\sim1900\rm\,K$, it peaks after secondary eclipse. We use the thermal structure from 3D global circulation models to determine the expected cloud distribution and Kepler lightcurves of hot Jupiters. We demonstrate that the change from an optical lightcurve dominated by thermal emission to one dominated by scattering (reflection) naturally explains the observed trend from negative to positive offset. For the cool planets the presence of an asymmetry in the Kepler lightcurve is a telltale sign of the cloud composition, because each cloud species can produce an offset only over a narrow range of effective temperatures. By comparing our models and the observations, we show that the cloud composition of hot Jupiters likely varies with equilibrium temperature. We suggest that a transition occurs between silicate and manganese sulfide clouds at a temperature near $1600\rm\,K$, analogous to the L/T transition on brown dwarfs. The cold trapping of cloud species below the photosphere naturally produces such a transition and predicts similar transitions for other condensates, including TiO. We predict that most hot Jupiters should have cloudy nightsides, that partial cloudiness should be common at the limb and that the dayside hot spot should often be cloud-free.

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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