New Formation Models for the Kepler-36 System
New Formation Models for the Kepler-36 System
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DOI：
10.3847/1538-4357/aae928
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发表时间：
2018-12-01
影响因子：
4.9
通讯作者：
D'Angelo, Gennaro
中科院分区：
文献类型：
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作者：
Bodenheimer, Peter;Stevenson, David J.;D'Angelo, Gennaro
开普勒-36系统中行星的形成是根据核心-核吸积情景通过详细的数值模拟来模拟的。标准模型被更新，包括在行星的气体包层中吸积的岩石星子的溶解，导致重元素包层质量的大量富集和深度不均匀的组成。对于kepler - 36c，考虑了原位形成模型和轨道迁移模型。结果与标准地层模型进行了比较。计算包括形成（吸积）阶段以及随后的冷却阶段，直到开普勒-36 （7 Gyr）的年龄。在后一阶段，包括恒星XUV辐射引起的质量损失。在所有情况下，结果都与kepler - 36c的测量质量（7.84 M-circle +）和半径（3.68 R-circle +）相吻合。为了获得这些拟合，需要改变两个参数：地层位置的盘状固体表面密度和XUV质量损失率中的“效率”因素。与标准模型相比，更新的模型温度更高，因此在地球的硅酸盐部分和上覆的H/He层中密度更低。较低的密度意味着只需要吸积一半的H/He就能满足目前的质量和半径限制。对于开普勒- 36b，最新的原位计算表明，在冷却阶段的早期，整个H/He包层都丢失了，这与观测结果一致。
Formation of the planets in the Kepler-36 system is modeled by detailed numerical simulations according to the core-nucleated accretion scenario. The standard model is updated to include the dissolution of accreting rocky planetesimals in the gaseous envelope of the planet, leading to substantial enrichment of the envelope mass in heavy elements and a non-uniform composition with depth. For Kepler-36 c, models involving in situ formation and models involving orbital migration are considered. The results are compared with standard formation models. The calculations include the formation (accretion) phase as well as the subsequent cooling phase, up to the age of Kepler-36 (7 Gyr). During the latter phase, mass loss induced by stellar XUV radiation is included. In all cases, the results fit the measured mass, 7.84 M-circle plus, and radius, 3.68 R-circle plus, of Kepler-36 c. Two parameters are varied to obtain these fits: the disk solid surface density at the formation location and the "efficiency" factor in the XUV mass-loss rate. The updated models are hotter and therefore less dense in the silicate portion of the planet and in the overlying layers of H/He, as compared with standard models. The lower densities mean that only about half as much H/He is needed to be accreted to fit the present-day mass and radius constraints. For Kepler-36 b, an updated in situ calculation shows that the entire H/He envelope is lost, early in the cooling phase, in agreement with observation.