Are exoplanetesimals differentiated?
Are exoplanetesimals differentiated?
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DOI：
10.1093/mnras/stz3603
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发表时间：
2020-02-01
影响因子：
4.8
通讯作者：
Harrison, John H. D.
中科院分区：
文献类型：
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作者：
Bonsor, Amy;Carter, Philip J.;Harrison, John H. D.
在白色矮星的大气层中观察到的金属表明，许多白矮星最近已经吸积了行星体。在某些情况下，观察到的成分表明主要来自分化行星体的核心（或地幔）的物质的吸积。不同系外行星间的碰撞产生了这样的碎片。在这项工作中，我们利用大量的白色矮星，其中至少有一个亲铁（核心爱好）和一个亲石（岩石爱好）的物种已被检测到评估如何共同exoplanetesimals分化。我们利用N-体模拟跟踪的命运的核心和地幔物质在行星系统的碰撞演化表明，大多数残余的分化星子保留核心分数类似于他们的父母，而有些是非常丰富的核心或地幔丰富。与白色矮星的钙和铁数据进行比较表明，这些数据与一个模型一致，其中66（-6）（+4）%的数据已吸积了已分化的微行星的残余物，而31（-5）（+5）%的Ca/Fe丰度因加热的影响而改变（尽管如果忽略加热，前者可能高达100%）。这些结论假设污染是由一个单一的天体造成的，并且碰撞演化在不同的行星系统中保留了相似的特征。这些结果表明，碰撞和分化是系外行星系统的关键过程。我们强调需要一个更大的样本污染的白色矮星精确确定的金属丰度，以更好地了解在系外行星系统的分化过程。
Metals observed in the atmospheres of white dwarfs suggest that many have recently accreted planetary bodies. In some cases, the compositions observed suggest the accretion of material dominantly from the core (or the mantle) of a differentiated planetary body. Collisions between differentiated exoplanetesimalrrs produce such fragments. In this work, we take advantage of the large numbers of white dwarfs where at least one siderophile (core-loving) and one lithophile (rock-loving) species have been detected to assess how commonly exoplanetesimals differentiate. We utilize N-body simulations that track the fate of core and mantle material during the collisional evolution of planetary systems to show that most remnants of differentiated planetesimals retain core fractions similar to their parents, while some are extremely core rich or mantle rich. Comparison with the white dwarf data for calcium and iron indicates that the data are consistent with a model in which 66(-6)(+4) per cent have accreted the remnants of differentiated planetesimals, while 31(-5)(+5) per cent have Ca/Fe abundances altered by the effects of heating (although the former can be as high as 100 per cent, if heating is ignored). These conclusions assume pollution by a single body and that collisional evolution retains similar features across diverse planetary systems. These results imply that both collisions and differentiation are key processes in exoplanetary systems. We highlight the need for a larger sample of polluted white dwarfs with precisely determined metal abundances to better understand the process of differentiation in exoplanetary systems.