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arXiv 1004.0696astro-ph.EPastro-ph.SR
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白矮星周围的尘埃云I：碎片云的起源

Dusty Disks around White Dwarfs I: Origin of Debris Disks

Ruobing Dong, Yan Wang, D. N. C. Lin, X. -W. Liu

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38 pages, 7 figures, single column, accepted by ApJ
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摘要：

相当一部分成熟的FGK恒星具有比太阳系外黄道光亮至少一个数量级的冷尘埃盘。由于这些尘埃必须不断补充，它们通常被认为是类似于柯伊伯带天体的残留星子的碰撞碎片。至少10%的太阳型恒星也有气体巨行星。拥有已知气体巨星或可探测到的碎片盘（或两者）的恒星比例似乎随着恒星质量的增加而增加。在这里，我们研究了长周期气体巨行星和残余星子系统的动力学演化，因为它们的宿主恒星演化出主序星，失去质量，并在残余白矮星核心周围形成行星状星云。遥远的气体巨行星和超千米大小的微行星的轨道会膨胀。在最强烈的AGB质量损失阶段，由于强烈的恒星风强烈的流体动力学阻力，亚米尺寸的粒子向它们的宿主恒星迁移。沿着它们的迁移路径，气体巨行星捕获并将亚公里大小的星子扫到它们的平均运动共振上。这些微行星也会获得适度的离心率，这取决于扰动行星的质量，恒星质量损失的速率和速度。被掠起的星子经历分裂性碰撞，导致产生具有扩展尺寸范围的颗粒。这些粒子上的辐射阻力对行星的共振屏障无效，它们形成30至150 AU大小的环，可以有效地以远红外连续谱的形式重新处理恒星辐射。我们确定了最近发现的尘埃环周围的白矮星WD 2226-210在中心的星云作为原型的磁盘，并建议这样的环可能是常见的。

英文摘要：

A significant fraction of the mature FGK stars have cool dusty disks at least an orders of magnitudes brighter than the solar system's outer zodiacal light. Since such dusts must be continually replenished, they are generally assumed to be the collisional fragments of residual planetesimals analogous to the Kuiper Belt objects. At least 10% of solar type stars also bear gas giant planets. The fraction of stars with known gas giants or detectable debris disks (or both) appears to increase with the stellar mass. Here, we examine the dynamical evolution of systems of long-period gas giant planets and residual planetesimals as their host stars evolve off the main sequence, lose mass, and form planetary nebula around remnant white dwarf cores. The orbits of distant gas giant planets and super-km-size planetesimals expand adiabatically. During the most intense AGB mass loss phase, sub-meter-size particles migrate toward their host stars due to the strong hydrodynamical drag by the intense stellar wind. Along their migration paths, gas giant planets capture and sweep up sub-km-size planetesimals onto their mean-motion resonances. These planetesimals also acquire modest eccentricities which are determined by the mass of the perturbing planets, the rate and speed of stellar mass loss. The swept-up planetesimals undergo disruptive collisions which lead to the production of grains with an extended size range. The radiation drag on these particles is ineffective against the planets' resonant barrier and they form 30-to-150-AU-sizes rings which can effective reprocess the stellar irradiation in the form of FIR continuum. We identify the recently discovered dust ring around the white dwarf WD 2226-210 at the center of the Helix nebula as a prototype of such disks and suggest such rings may be common.

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