论文标题
白矮人污染由水合的行星残留物：WD J204713.76-125908.9中的氢和金属
White dwarf pollution by hydrated planetary remnants: Hydrogen and Metals in WD J204713.76-125908.9
论文作者
论文摘要
WD J204713.76-125908.9是一类带有氦气为主导的光电的小型白色矮人的新成员，具有强烈的Balmer吸收线和大气金属污染。在这些恒星中观察到的氢的特殊丰度可能是水丰富的岩石体积聚的结果。我们在非常大的望远镜上使用宇宙起源光谱仪在板载上获得了WD J204713.76-125908.9的遥远脱硫器和光谱，并在非常大的望远镜上获得了X-Shooter。丰度比与富含挥发性元件的碳和氧的外样碎屑的稳态积聚，以及与散装土相比，分别为十七，两个和四个因素，分别为17，两个和四个因素。母体具有类似于太阳系碳质软管的组成，而推断的最小质量为$ 1.6 \ times 10^{20} $ G，与半径23 km的小行星相当。我们对破坏的母体的组成进行建模，从模拟中发现中位水量分数为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 the Hubble Space Telescope and 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 seventeen, two, and four respectively compared to bulk Earth. The parent body has a composition akin to Solar System carbonaceous chondrites, and the inferred minimum mass, $1.6 \times 10^{20}$ g, 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 eight per cent.
