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Bayesian constraints on the origin and geology of exoplanetary material using a population of externally polluted white dwarfs
Monthly Notices of the Royal Astronomical Society ( IF 4.7 ) Pub Date : 2021-03-23 , DOI: 10.1093/mnras/stab736
John H D Harrison 1 , Amy Bonsor 1 , Mihkel Kama 1, 2, 3 , Andrew M Buchan 1 , Simon Blouin 4 , Detlev Koester 5
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White dwarfs that have accreted planetary bodies are a powerful probe of the bulk composition of exoplanetary material. In this paper, we present a Bayesian model to explain the abundances observed in the atmospheres of 202 DZ white dwarfs by considering the heating, geochemical differentiation, and collisional processes experienced by the planetary bodies accreted, as well as gravitational sinking. The majority (>60 per cent) of systems are consistent with the accretion of primitive material. We attribute the small spread in refractory abundances observed to a similar spread in the initial planet-forming material, as seen in the compositions of nearby stars. A range in Na abundances in the pollutant material is attributed to a range in formation temperatures from below 1000 K to higher than 1400 K, suggesting that pollutant material arrives in white dwarf atmospheres from a variety of radial locations. We also find that Solar System-like differentiation is common place in exoplanetary systems. Extreme siderophile (Fe, Ni, or Cr) abundances in eight systems require the accretion of a core-rich fragment of a larger differentiated body to at least a 3σ significance, whilst one system shows evidence that it accreted a crust-rich fragment. In systems where the abundances suggest that accretion has finished (13/202), the total mass accreted can be calculated. The 13 systems are estimated to have accreted masses ranging from the mass of the Moon to half that of Vesta. Our analysis suggests that accretion continues for 11 Myrs on average.

中文翻译:

使用外部污染的白矮星群体对系外行星物质的起源和地质学进行贝叶斯约束

具有吸积行星体的白矮星是对系外行星物质整体成分的有力探测。在本文中,我们提出了一个贝叶斯模型,通过考虑吸积的行星体所经历的加热、地球化学分化和碰撞过程以及重力下沉来解释在 202 DZ 白矮星大气中观察到的丰度。大多数(>60%)系统与原始物质的吸积相一致。我们将观察到的耐火材料丰度的小幅分布归因于初始行星形成材料中的类似分布,如附近恒星的组成所示。污染物材料中 Na 丰度的范围归因于从低于 1000 K 到高于 1400 K 的地层温度范围,表明污染物物质从各种径向位置到达白矮星大气。我们还发现,类似太阳系的分化在系外行星系统中很常见。八个系统中的极端亲铁元素(Fe、Ni 或 Cr)丰度需要将较大分化体的富含核心的碎片吸积到至少 3σ 显着性,而一个系统显示出它吸积了富含地壳的碎片的证据。在丰度表明吸积已经完成的系统中(13/202),可以计算吸积的总质量。据估计,这 13 个系统的吸积质量从月球质量到灶神星质量的一半不等。我们的分析表明,平均增加 11 Myrs。我们还发现,类似太阳系的分化在系外行星系统中很常见。八个系统中的极端亲铁元素(Fe、Ni 或 Cr)丰度需要将较大分化体的富含核心的碎片吸积到至少 3σ 显着性,而一个系统显示出它吸积了富含地壳的碎片的证据。在丰度表明吸积已经完成的系统中(13/202),可以计算吸积的总质量。据估计,这 13 个系统的吸积质量从月球质量到灶神星质量的一半不等。我们的分析表明,平均增加 11 Myrs。我们还发现,类似太阳系的分化在系外行星系统中很常见。八个系统中的极端亲铁元素(Fe、Ni 或 Cr)丰度需要将较大分化体的富含核心的碎片吸积到至少 3σ 显着性,而一个系统显示出它吸积了富含地壳的碎片的证据。在丰度表明吸积已经完成的系统中(13/202),可以计算吸积的总质量。据估计,这 13 个系统的吸积质量从月球质量到灶神星质量的一半不等。我们的分析表明,平均增加 11 Myrs。而一个系统显示有证据表明它吸积了一个富含地壳的碎片。在丰度表明吸积已经完成的系统中(13/202),可以计算吸积的总质量。据估计,这 13 个系统的吸积质量从月球质量到灶神星质量的一半不等。我们的分析表明,平均增加 11 Myrs。而一个系统显示有证据表明它吸积了一个富含地壳的碎片。在丰度表明吸积已经完成的系统中(13/202),可以计算吸积的总质量。据估计,这 13 个系统的吸积质量从月球质量到灶神星质量的一半不等。我们的分析表明,平均增加 11 Myrs。
更新日期:2021-03-23
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