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arXiv 2109.13487astro-ph.EP
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通过巨大撞击和光蒸发近距离超级地球的尺寸演化

Size evolution of close-in super-Earths through giant impacts and photoevaporation

Yuji Matsumoto, Eiichiro Kokubo, Pin-Gao Gu, Kenji Kurosaki

摘要:

开普勒过境调查与后续光谱观测发现了许多超级地球大小的行星,并揭示了它们的大小,轨道周期及其相邻行星之间的关系的有趣特征。这是我们第一次通过巨大的撞击和光蒸发来研究行星的大小演化,并与这些观测到的特征进行比较。我们通过分析模型计算了原行星的大小,即其核心和包层大小的总和。$N$体模拟进行演变行星的大小在巨大的影响阶段与包络剥离通过冲击。我们考虑核心质量的初始径向轮廓和初始包层质量分数作为参数。内部行星可能会通过巨大的撞击失去它们的整个包络,而外部行星可以保持它们的初始包络,因为它们不会经历巨大的撞击。光蒸发被模拟为之后演化行星的大小。我们的研究结果表明,观察到的行星的周期半径分布将被复制,如果我们进行模拟,其中的核心质量的初始径向分布遵循广泛的幂律分布和初始包络质量分数是$\sim0.1$。此外,我们的模型显示,相邻的行星对具有相似的大小和规则的间距,与详细的观测结果略有差异,如半径差距。

英文摘要:

The Kepler transit survey with follow-up spectroscopic observations has discovered numerous super-Earth sized planets and revealed intriguing features of their sizes, orbital periods, and their relations between adjacent planets. For the first time, we investigate the size evolution of planets via both giant impacts and photoevaporation to compare with these observed features. We calculate the size of a protoplanet, which is the sum of its core and envelope sizes, by analytical models. $N$-body simulations are performed to evolve planet sizes during the giant impact phase with envelope stripping via impact shocks. We consider the initial radial profile of the core mass and the initial envelope mass fractions as parameters. Inner planets can lose their whole envelopes via giant impacts, while outer planets can keep their initial envelopes since they do not experience giant impacts. Photoevaporation is simulated to evolve planet sizes afterward. Our results suggest that the period-radius distribution of the observed planets would be reproduced if we perform simulations in which the initial radial profile of the core mass follows a wide range of power-law distributions and the initial envelope mass fractions are $\sim0.1$. Moreover, our model shows that the adjacent planetary pairs have similar sizes and regular spacings, with slight differences from detailed observational results such as the radius gap.

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