系外行星宿主星的锂丰度：模拟
Lithium abundances in exoplanet-host stars : modelling
摘要：
目标。已知系外行星宿主恒星（EHS）表面的化学丰度与没有探测到行星的恒星（NEHS）不同。平均而言，EHS与太阳相比金属含量过高。观测结果还表明，对于冷恒星，锂在EHS中比在NEHS中更耗尽。本文的目的是获得限制可能的模型能够解释这种差异，在overmetallic模型的框架相比，太阳能丰度的模型。方法.我们计算了不同质量和金属丰度的主序星模型。结果表明，根据这些参数，锂的破坏行为不同。我们将这些结果与锂的光谱观测进行了比较。结果我们的模型表明，EHS和NEHS之间观察到的锂差异并不直接归因于EHS的金属过剩：对流区下方需要一些额外的混合。我们讨论了可能的解释所需的额外的混合，特别是与对流区以下的剪切不稳定性的发展相关联的混合效率的增加，触发角动量转移由于行星迁移。
英文摘要：
Aims. Exoplanet-host stars (EHS) are known to present superficial chemical abundances different from those of stars without any detected planet (NEHS). EHS are, on the average, overmetallic compared to the Sun. The observations also show that, for cool stars, lithium is more depleted in EHS than in NEHS. The aim of this paper is to obtain constraints on possible models able to explain this difference, in the framework of overmetallic models compared to models with solar abundances. Methods. We have computed main sequence stellar models with various masses and metallicities. The results show different behaviour for the lithium destruction according to those parameters. We compare these results to the spectroscopic observations of lithium. Results. Our models show that the observed lithium differences between EHS and NEHS are not directly due to the overmetallicity of the EHS: some extra mixing is needed below the convective zones. We discuss possible explanations for the needed extra mixing, in particular an increase of the mixing efficiency associated with the development of shear instabilities below the convective zone, triggered by angular momentum transfer due to the planetary migration.
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