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arXiv 1004.4649astro-ph.SR
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CoRoT系外行星宿主星中难熔和挥发性元素的分布

Distribution of refractory and volatile elements in CoRoT exoplanet host stars

C. Chavero, R. de la Reza, R. C. Domingos, N. A. Drake, C. B. Pereira, O. C. Winter

摘要:

恒星与行星之间难熔、中间和挥发性元素丰度的相对分布可以作为研究巨行星内部迁移的重要工具。这种迁移可以导致星子的吸积,以及恒星对这些元素的选择性富集。我们报告的光谱测定的大气参数和化学丰度的母星过境行星CoRoT-2b和CoRoT-4 b。添加来自文献的CoRoT-3和CoRoT-5的数据,我们发现相对丰度作为其冷凝温度的函数的平坦分布。对于CoRoT-2,相对较高的锂丰度和Li I共振线的强度使我们能够提出1.2亿年的年龄,使这颗恒星成为迄今为止最年轻的恒星之一。我们引入了一种新的方法来研究这些恒星的丰度和它们的行星的内部迁移之间的关系。通过模拟行星在仅由微行星形成的盘中的内部迁移,我们能够分离吸积到中央恒星上的难熔(R),中间(I)和挥发性(V)丰富的微行星的恒星部分。富集恒星的中间元素和挥发性元素组分与纯难熔元素组分相似且远大于纯难熔元素组分。我们还表明,这些结果是高度依赖于所采用的磁盘分布区域的R,I,V元素和其他参数的模型。然而,我们注意到,这种自富集机制只有在盘的生命周期的第一个20-30百万年或以后,当中央恒星的表面对流层第一次达到其最小尺寸配置时才有效。

英文摘要:

The relative distribution of abundances of refractory, intermediate, and volatile elements in stars with planets can be an important tool for investigating the internal migration of a giant planet. This migration can lead to the accretion of planetesimals and the selective enrichment of the star with these elements. We report on a spectroscopic determination of the atmospheric parameters and chemical abundances of the parent stars in transiting planets CoRoT-2b and CoRoT-4b. Adding data for CoRoT-3 and CoRoT-5 from the literature, we find a flat distribution of the relative abundances as a function of their condensation temperatures. For CoRoT-2, the relatively high lithium abundance and intensity of its Li I resonance line permit us to propose an age of 120 Myr, making this stars one of the youngest stars with planets to date. We introduce a new methodology to investigate a relation between the abundances of these stars and the internal migration of their planets. By simulating the internal migration of a planet in a disk formed only by planetesimals, we are able to separate the stellar fractions of refractory (R), intermediate (I), and volatile (V) rich planetesimals accreting onto the central star. Intermediate and volatile element fractions enriching the star are similar and much larger than those of pure refractory ones. We also show that these results are highly dependent on the model adopted for the disk distribution regions in terms of R, I, and V elements and other parameters considered. We note however, that this self-enrichment mechanism is only efficient during the first 20-30 Myr or later in the lifetime of the disk when the surface convection layers of the central star for the first time attain its minimum size configuration.

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