白矮星周围富含金属的碎片盘
Metal-rich debris discs around white dwarfs
摘要：
我们已经发现了两个中等温度（~18000- 22000 K）的白矮星，SDSSJ 1228 +1040和SDSSJ 1043 +0855，它们在CaII 8600 A三重态中具有双峰发射线。这些谱线轮廓是外半径为~ 1 Rsun的气体盘围绕两颗白矮星运行的明确特征。这两颗恒星都是从星周物质中吸积而来，导致光球层中镁的丰度很大。圆盘中没有氢的释放，而白矮星光球中也没有氦的吸收，这表明星周物质中的挥发性元素已经耗尽，这些气体环最有可能的来源是潮汐破裂的岩石小行星。SDSSJ 1228 +1040相对较高的质量意味着行星系统不仅可以在4- 5百万太阳系恒星周围形成，而且可能在主序星后演化中幸存下来。
英文摘要：
We have identified two moderately hot (~18000-22000K) white dwarfs, SDSSJ1228+1040 and SDSSJ1043+0855, which exhibit double-peaked emission lines in the CaII 8600A triplet. These line profiles are unambiguous signatures of gaseous discs with outer radii of ~1Rsun orbiting the two white dwarfs. Both stars accrete from the circumstellar material, resulting in large photospheric Mg abundances. The absence of hydrogen emission from the discs, and helium absorption in the white dwarf photospheres demonstrates that the circumstellar material is depleted in volatile elements, and the most likely origin of these gaseous rings are tidally disrupted rocky asteroids. The relatively high mass of SDSSJ1228+1040 implies that planetary systems can not only form around 4-5Msun stars, but may also survive their post main-sequence evolution.
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