在开放的星团中通过近距离恒星相遇剥离碎片盘
Stripping a debris disk by close stellar encounters in an open stellar cluster
摘要：
碎片盘是围绕主序星的任何行星系统的组成部分。我们研究近距离的恒星相遇是否可以破坏和剥离其星子在其诞生的不断扩大的疏散星团与恒星数密度下降超过100万年的碎片盘。这种剥离会影响尘埃的产生，从而影响磁盘的可探测性。我们列出了在100和1000天文单位之间的错过距离恒星飞掠期间剥离的星子的分数，并为几个质量比的中心通过恒星。然后，我们估计了几个以初始恒星密度为特征的膨胀疏散星团一生中近距离恒星相遇的数量。我们发现，对于一个标准的盘，其内外半径分别为40和100天文单位，在恒星密度小于1000 pc^-3的普通嵌入星团中诞生的恒星周围，超过1亿年的星子不会损失。与此相反，我们发现，在猎户座型星团中诞生的恒星周围，恒星密度大于20 000 pc^-3的恒星在这一时间尺度上会严重耗尽其星子。在这样的环境下，超过1亿年，一个盘在M矮星周围会损失超过97%的星子，在太阳型恒星周围会损失超过63%，在A矮星周围会损失超过42%。我们粗略估计，三分之二的恒星可能诞生在这样高密度的星团中。这可能部分解释了为什么在低质量恒星周围观察到的碎片盘较少。
英文摘要：
A debris disk is a constituent of any planetary system surrounding a main sequence star. We study whether close stellar encounters can disrupt and strip a debris disk of its planetesimals in the expanding open cluster of its birth with a decreasing star number density over 100 Myrs. Such stripping would affect the dust production and hence detectability of the disk. We tabulated the fractions of planetesimals stripped off during stellar flybys of miss distances between 100 and 1000 AU and for several mass ratios of the central to passing stars. We then estimated the numbers of close stellar encounters over the lifetime of several expanding open clusters characterized by their initial star densities. We found that a standard disk, with inner and outer radii of 40 and 100 AU, suffers no loss of planetesimals over 100 Myrs around a star born in a common embedded cluster with star density <1000 pc^-3. In contrast, we found that such a disk is severely depleted of its planetesimals over this timescale around a star born in an Orion-type cluster where the star density is >20 000 pc^-3. In this environment, a disk loses >97% of its planetesimals around an M-dwarf, >63% around a solar-type star, and >42% around an A-dwarf, over 100 Myrs. We roughly estimate that two-thirds of the stars may be born in such high star density clusters. This might explain in part why fewer debris disks are observed around lower mass stars.
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