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arXiv 1102.1719astro-ph.SRastro-ph.GA
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晚型双星的初始周期函数及其变化

The initial period function of late-type binary stars and its variation

Pavel Kroupa, Monika G. Petr-Gotzens

摘要:

研究了晚型双星周期分布函数的变化。它表明,金牛座-御夫座前主序列人口和主序列G矮样本不来自同一个母周期分布,置信概率超过95%。狼疮、上天蝎座A和金牛座-御夫座群体被证明与从相同的初始周期函数(IPF)得出的结果兼容,这与主序列数据不一致。两种可能的IPF形式被用来找到现有数据的各种排列的母分布,包括上天蝎座B(USCB),变色龙和猎户座星云星团前主序列样本。这里研究的所有主序前样本都与假设一致,即存在一个普遍的IPF,如果它形成于嵌入星团中,则通过双星破坏进行修改,从而导致观测到的周期函数随周期增加而普遍下降。主序星前的数据承认对数正态IPF与Duquennoy & Mayor(1991)得出的主序星IPF相似,前提是主序星前的双星比例明显更高。但是,为了与原恒星数据保持一致,可能的普适IPF在log-P或log-半长轴上应该是平坦的,并且必须与通过逆动力学布居合成得到的K1 IPF形式相似,如果大多数恒星形成于典型的嵌入星团中,这已经被证明会导致主序星周期函数。

英文摘要:

The variation of the period distribution function of late-type binaries is studied. It is shown that the Taurus--Auriga pre-main sequence population and the main sequence G dwarf sample do not stem from the same parent period distribution with better than 95 per cent confidence probability. The Lupus, Upper Scorpius A and Taurus--Auriga populations are shown to be compatible with being drawn from the same initial period function (IPF), which is inconsistent with the main sequence data. Two possible IPF forms are used to find parent distributions to various permutations of the available data which include Upper Scorpius B (UScB), Chameleon and Orion Nebula Cluster pre-main sequence samples. All the pre-main sequence samples studied here are consistent with the hypothesis that there exists a universal IPF which is modified through binary-star disruption if it forms in an embedded star cluster leading to a general decline of the observed period function with increasing period. The pre-main sequence data admit a log-normal IPF similar to that arrived at by Duquennoy & Mayor (1991) for main sequence stars, provided the binary fraction among pre-main sequence stars is significantly higher. But, for consistency with proto-stellar data, the possibly universal IPF ought to be flat in log-P or log-semi-major axis and must be similar to the K1 IPF form derived through inverse dynamical population synthesis, which has been shown to lead to the main sequence period function if most stars form in typical embedded clusters.

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