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arXiv 1111.5478astro-ph.EP
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强辐射巨行星的昼夜侧核冷却

Day and night side core cooling of a strongly irradiated giant planet

J. Budaj, I. Hubeny, A. Burrows

摘要:

行星内部的热量损失或冷却决定了它的结构和演化。我们研究了辐射,大气的金属含量,热量再分配,平流层,以及热量再分配发生在大气结构,核心熵的深度,以及随后对行星内部冷却的影响。我们地址在一个一致的方式之间的耦合的白天和黑夜的一个星球的热量再分配模型大气计算的装置。我们假设,强对流导致相同的熵在白天和黑夜的一面,重力是相同的两个半球。我们认为,核心冷却率从两个半球的强烈照射的行星可能是不一样的,差异取决于几个重要的参数。如果昼夜热再分配非常有效,或者如果它发生在大的光学深度,那么白天侧和夜晚侧的冷却可能是可比的。然而,如果昼夜热传输效率不高,或者如果它发生在较浅的光学深度处,则白天和夜晚侧冷却之间可能存在很大的差异,并且夜晚侧将更有效地冷却。如果恒星的辐射变得更强,例如由于恒星演化或迁移,来自白天和黑夜的冷却都会减少。大气中金属含量的增加将作为一个额外的"毯子",减少白天和夜晚的冷却。然而,行星昼侧的平流层可以增强昼侧的冷却,因为它的不透明度可以作为屏蔽恒星辐射的“屏障”。这些效应也可能影响相互作用双星中著名的重力暗化和辐射热互扰效应,特别是对于强辐射的冷组分。

英文摘要:

The internal heat loss, or cooling, of a planet determines its structure and evolution. We study the effects of irradiation, metallicity of the atmosphere, heat redistribution, stratospheres, and the depth where the heat redistribution takes place on the atmospheric structure, the core entropy, and subsequently on the cooling of the interior of the planet. We address in a consistent fashion the coupling between the day and the night sides of a planet by means of model atmosphere calculations with heat redistribution. We assume that strong convection leads to the same entropy on the day and night sides and that gravity is the same on both hemispheres. We argue that the core cooling rates from the two hemispheres of a strongly irradiated planet may not be the same and that the difference depends on several important parameters. If the day-night heat redistribution is very efficient or if it takes place at the large optical depth, then the day-side and the night-side cooling may be comparable. However, if the day-night heat transport is not efficient or if it takes place at a shallow optical depth then there can be a large difference between the day- and the night-side cooling and the night side will cool more efficiently. If stellar irradiation becomes stronger, e.g. owing to stellar evolution or migration, cooling from both the day and the night sides is reduced. Enhanced metallicity of the atmosphere would act as an added "blanket" and reduces both the day- and the night-side cooling. However, a stratosphere on the planetary day side can enhance day-side cooling since its opacity acts as a "sunshade" that screens the stellar irradiation. These effects may also influence the well-known gravity darkening and bolometric albedo effects in interacting binaries, especially for strongly irradiated cold components.

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