TWO EXTRASOLAR ASTEROIDS WITH LOW VOLATILE-ELEMENT MASS FRACTIONS
TWO EXTRASOLAR ASTEROIDS WITH LOW VOLATILE-ELEMENT MASS FRACTIONS
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两颗低挥发元素质量分数的太阳系外小行星
DOI：
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发表时间：
2012
期刊：
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通讯作者：
U. Kiel
中科院分区：
文献类型：
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作者：
M. Jura;S. Xu;B. Klein;D. Koester;B. Zuckerman;Ucla;U. Kiel
利用哈勃太空望远镜上的宇宙起源光谱仪获得的紫外光谱，我们扩展了我们以前的地面光学测定的太阳系外小行星的组成吸积到两个白色矮星，GD 40和G241-6。结合这些恒星的光学和紫外光谱与氦占主导地位的大气，13和12个污染元素分别在GD 40和G241-6中被确信地检测到。对于GD 40上的物质，挥发性元素C和S与原始CI陨石中的质量分数相比不足10倍以上，N至少不足5倍，并接近大块地球的推断。G241-6也有类似的模式，只是S未耗尽。我们还新发现或放置有意义的上限的量的Cl，Al，P，Ni和Cu的吸积物质。从光学研究的结果延伸，难熔元素在吸积母体的质量分数是相似的散装地球和陨石测量。热处理，也许内部的雪线，似乎是至关重要的，在确定这些特定的太阳系外小行星的元素组成。
Using ultraviolet spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, we extend our previous ground-based optical determinations of the composition of the extrasolar asteroids accreted onto two white dwarfs, GD 40 and G241-6. Combining optical and ultraviolet spectra of these stars with He-dominated atmospheres, 13 and 12 polluting elements are confidently detected in GD 40 and G241-6, respectively. For the material accreted onto GD 40, the volatile elements C and S are deficient by more than a factor of 10 and N by at least a factor of 5 compared to their mass fractions in primitive CI chondrites and approach what is inferred for bulk Earth. A similar pattern is found for G241-6 except that S is undepleted. We have also newly detected or placed meaningful upper limits for the amount of Cl, Al, P, Ni, and Cu in the accreted matter. Extending results from optical studies, the mass fractions of refractory elements in the accreted parent bodies are similar to what is measured for bulk Earth and chondrites. Thermal processing, perhaps interior to a snow line, appears to be of central importance in determining the elemental compositions of these particular extrasolar asteroids.