行星吞噬是白矮星污染的触发器
Planetary engulfment as a trigger for white dwarf pollution
摘要：
一个行星系的存在可以保护一个小行星盘免受来自遥远的大质量外天体（行星或恒星伴星）的长期引力扰动。当主星脱离主序星演化成白矮星时，这些行星可能被吞没，引发长期不稳定性，导致小型岩石天体的潮汐破裂。这些破裂的天体可以为白矮星提供岩石物质，并可能解释其大气中的高金属含量物质。我们说明了这种机制可以操作时，引力摄动是由于Kozai-Lidov机制从恒星双星伴侣。我们表明，这种机制可以解释所观察到的吸积水平，如果：（1）行星吞没发生快速相比，长期的时间尺度，这是一般的情况下，宽双星（$>100$ AU）和行星吞没在渐近巨星分支;（2）星子盘有一个总质量为$\sim10^{-4}-10^{-2}M_\oplus$。我们表明，这种新的机制可以提供一个稳定的供应的材料在整个生命周期的白矮星的所有冷却年龄，并可以占很大一部分（近一半）所观察到的污染WD。
英文摘要：
The presence of a planetary system can shield a planetesimal disk from the secular gravitational perturbations due to distant outer massive objects (planets or stellar companions). As the host star evolves off the main sequence to become a white dwarf, these planets can be engulfed, triggering secular instabilities and leading to the tidal disruptions of small rocky bodies. These disrupted bodies can feed the white dwarfs with rocky material and possibly explain the high-metallicity material in their atmospheres. We illustrate how this mechanism can operate when the gravitational perturbations are due to the Kozai-Lidov mechanism from a stellar binary companion. We show that this mechanism can explain the observed levels of accretion if: (1) the planetary engulfment happens fast compared to the secular timescale, which is generally the case for wide binaries ($>100$ AU) and planetary engulfment during the Asymptotic Giant Branch; (2) the planetesimal disk has a total mass of $\sim10^{-4}-10^{-2}M_\oplus$. We show that this new mechanism can provide a steady supply of material throughout the entire life of the white dwarfs for all cooling ages and can account for a large fraction (up to nearly half) of the observed polluted WDs.
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