On the properties of young multiple stars
On the properties of young multiple stars
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论年轻多星的性质
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
S. Hodgkin
中科院分区：
文献类型：
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作者：
E. Delgado;C. Clarke;M. Bate;S. Hodgkin
我们提出了年轻的二进制和多恒星系统的性质的数值结果。我们的分析是基于一系列的平滑粒子流体动力学（SPH）+N体模拟的小分子云，完全解决了不透明度限制的碎片。这些模拟结果表明，多个星星的形成是一个主要的渠道，星星的形成在湍流。我们已经产生了一个稳定的多个系统的统计上显着的数量，与范围内的101 -103 Au的组分分离。在流体动力学阶段（0.5百万年）结束时，我们发现60%的恒星和褐矮星是多重系统的成员，其中约三分之一是低质量，弱约束的离群者，在宽偏心轨道上。我们的研究结果意味着，在恒星制度，大多数恒星的倍数（1080%），这部分是一个增加的功能的主要质量。在N体整合到1050万年后，束缚天体的百分比下降到大约40%，这种下降主要来自于被释放到场中的非常低质量的恒星和褐矮星。棕矮星从来没有被发现是恒星非常接近的伴星（棕矮星沙漠在非常小的分离），但有一个例子存在棕矮星伴星在中间分离（10 Au）。我们的模拟可以容纳在大分离的棕矮星同伴的存在，但只有当这些系统的原色本身是倍数。
我们比较了我们的模拟结果与真实的恒星系统的属性推导出的红外色星等图的Praesepe集群和光谱和高分辨率成像调查的年轻的集群和字段。我们发现，所观察到的Praesepe主序在0.4-1 M的范围内的传播似乎需要恒星确实通常组装成高阶多系统。类似地，对金牛座和蛇夫座ρ，或者像长蛇座TW和MBM 12这样的移动星系群的观测结果表明，年轻系统中的伴星频率确实可以像我们预测的那样高。与观测资料的比较也说明了模拟结果中存在的两个问题。首先，低质量比（q < 0.2）的双星不是由我们的模型产生的，与Praesepe色星等图和来自实地双星调查的独立证据相冲突。其次，我们的模拟显示，非常低质量的恒星和褐矮星双星似乎生产不足。
We present numerical results on the properties of young binary and multiple stellar systems. Our analysis is based on a series of smoothed particle hydrodynamics (SPH) +N-body simulations of the fragmentation of small molecular clouds, which fully resolve the opacity limit for fragmentation. These simulations demonstrate that multiple star formation is a major channel for star formation in turbulent flows. We have produced a statistically significant number of stable multiple systems, with component separations in the range ∼1–103 au. At the end of the hydrodynamic stage (0.5 Myr), we find that ≈60 per cent of stars and brown dwarfs are members of multiples systems, with about a third of these being low-mass, weakly bound outliers in wide eccentric orbits. Our results imply that in the stellar regime most stars are in multiples (≈80 per cent) and that this fraction is an increasing function of primary mass. After N-body integration to 10.5 Myr, the percentage of bound objects has dropped to about 40 per cent, this decrease arising mostly from very low-mass stars and brown dwarfs that have been released into the field. Brown dwarfs are never found to be very close companions to stars (the brown dwarf desert at very small separations), but one case exists of a brown dwarf companion at intermediate separations (10 au). Our simulations can accommodate the existence of brown dwarf companions at large separations, but only if the primaries of these systems are themselves multiples.
We have compared the outcome of our simulations with the properties of real stellar systems as deduced from the infrared colour–magnitude diagram of the Praesepe cluster and from spectroscopic and high-resolution imaging surveys of young clusters and the field. We find that the spread of the observed main sequence of Praesepe in the 0.4–1 M⊙ range appears to require that stars are indeed commonly assembled into high-order multiple systems. Similarly, observational results from Taurus and ρ Ophiuchus, or moving groups such as TW Hydrae and MBM 12, suggest that companion frequencies in young systems can indeed be as high as we predict. The comparison with observational data also illustrates two problems with the simulation results. First, low mass ratio (q < 0.2) binaries are not produced by our models, in conflict with both the Praesepe colour–magnitude diagram and independent evidence from field binary surveys. Secondly, very low-mass stars and brown dwarf binaries appear to be considerably underproduced by our simulations.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell