英澳行星搜索中观测到的光谱双星分布
The Observed Distribution of Spectroscopic Binaries from the Anglo-Australian Planet Search
摘要：
我们报告的16个双系统的检测从英澳行星搜索。径向速度数据的解表明，恒星有伴星，它们的质量、偏心率和周期都有很大的变化。其中三个系统可能包含棕矮星伴星，而另外两个系统的偏心率使它们处于周期小于1000 d的双星偏心率分布的极端上尾。在长达12年的时间里，我们的伴星质量分布相当平坦，反映了其他径向速度调查中所看到的情况，并与目前候选行星质量的分布形成鲜明对比，后者在10 MJ以下强烈上升。当观察一个更大的样本的二进制文件，具有FGK恒星原色作为一个函数的主要恒星金属丰度，我们发现，分布保持一个43 $\pm$ 4%的二进制部分之间的金属丰度-1.0至+0.6 dex。这与巨大的系外行星分布形成鲜明对比。这一结果与双星形成模型相吻合，该模型认为这是一个坍缩的巨大分子云的碎片，这表明这是近距离双星的主要形成机制，而不是主星残留的原行星盘的碎片。
英文摘要：
We report the detection of sixteen binary systems from the Anglo-Australian Planet Search. Solutions to the radial velocity data indicate that the stars have companions orbiting with a wide range of masses, eccentricities and periods. Three of the systems potentially contain brown-dwarf companions while another two have eccentricities that place them in the extreme upper tail of the eccentricity distribution for binaries with periods less than 1000 d. For periods up to 12 years, the distribution of our stellar companion masses is fairly flat, mirroring that seen in other radial velocity surveys, and contrasts sharply with the current distribution of candidate planetary masses, which rises strongly below 10MJ. When looking at a larger sample of binaries that have FGK star primaries as a function of the primary star metallicity, we find that the distribution maintains a binary fraction of ~43$\pm$4% between -1.0 to +0.6 dex in metallicity. This is in stark contrast to the giant exoplanet distribution. This result is in good agreement with binary formation models that invoke fragmentation of a collapsing giant molecular cloud, suggesting this is the dominant formation mechanism for close binaries and not fragmentation of the primary star's remnant proto-planetary disk.
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