White dwarf pollution by hydrated planetary remnants: hydrogen and metals in WD J204713.76-125908.9
White dwarf pollution by hydrated planetary remnants: hydrogen and metals in WD J204713.76-125908.9
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水合行星残余物造成的白矮星污染：WD J204713.76-125908.9 中的氢和金属
DOI：
10.1093/mnras/staa2717
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发表时间：
2020
影响因子：
4.8
通讯作者：
Hoskin M
中科院分区：
文献类型：
--
作者：
Hoskin M
WD J204713.76-125908.9是一个新加入的小类白色矮星与氦为主的光球，表现出强的巴耳末吸收线和大气金属污染。在这些恒星中观测到的异常丰富的氢可能是富含水的岩石天体吸积的结果。我们利用哈勃空间望远镜上的宇宙起源摄谱仪和甚大望远镜上的X射线摄影仪获得了WD J204713.76-125908.9的远紫外光谱和光学光谱，并确定了9种金属的光球吸收线：C，O，Mg，Si，P，S，Ca，Fe和Ni。丰度比与富含挥发性元素碳和氧以及过渡元素硫的系外行星小碎片的稳态吸积一致，与地球本体相比，分别是17、2和4倍。其母体的组成类似于太阳系的碳质陨石，推断的最小质量为1.6 × 1020克，相当于半径为23公里的小行星。我们模拟了被破坏的母体的组成，从我们的模拟中发现水的质量分数中位数为8%。
WD J204713.76–125908.9 is a new addition to the small class of white dwarfs with helium-dominated photospheres that exhibit strong Balmer absorption lines and atmospheric metal pollution. The exceptional abundances of hydrogen observed in these stars may be the result of accretion of water-rich rocky bodies. We obtained far-ultraviolet and optical spectroscopy of WD J204713.76–125908.9 using the Cosmic Origin Spectrograph on-board theHubble Space Telescopeand X-shooter on the Very Large Telescope, and identify photospheric absorption lines of nine metals: C, O, Mg, Si, P, S, Ca, Fe, and Ni. The abundance ratios are consistent with the steady-state accretion of exo-planetesimal debris rich in the volatile elements carbon and oxygen, and the transitional element sulphur, by factors of 17, 2, and 4, respectively, compared to the bulk Earth. The parent body has a composition akin to Solar system carbonaceous chondrites, and the inferredminimummass, 1.6 × 1020g, is comparable to an asteroid 23 km in radius. We model the composition of the disrupted parent body, finding from our simulations a median water mass fraction of 8 per cent.