The multiplicity of newborn high-mass stars

大质量恒星（质量超过10个太阳质量）的起源是恒星形成中尚未解决的主要问题之一，也是目前争论激烈的主题。虽然大质量恒星的初始质量函数一直被认为是一个重要的话题，但对大质量恒星的双星特性的研究却少得多。然而，越来越明显的是，只有少数大质量恒星是单一的，它们甚至可能是动态溶解的双星系统的一部分。因此，理解大质量恒星的形成等同于理解大质量双星的形成。猎户座四边形中大质量恒星的伴星比例为1.5，而猎户座中低质量恒星的伴星比例为0.5。这种差异是一个强有力的指标，表明高质量和低质量双星的形成可能是不同的，而且大质量恒星的形成不太可能仅仅是低质量恒星形成的放大版本。至少有四种不同的假设被提出来解释大质量双星的诞生：(1)大质量恒星周围的大质量圆盘的破碎，(2)低质量原双星的邦迪-霍伊尔吸积，(3)密集星团中中等质量原恒星的相遇和潮汐捕获，以及(4)密集星团中的动态三体捕获。为了验证这些理论，我们需要对非常年轻的大质量恒星的双子星有更全面的了解，那时动力学相互作用还没有完全发挥出来。我们建议对猎户座OB1星协中大约80颗大质量恒星进行系统的研究，寻找双星，并确定它们的特征。然后，理论学家可以将这些材料与他们对上面列出的大质量双星形成的四种假设的预测进行比较。此外，我们注意到，这些OB恒星中只有少数进行了初步的大气模拟，我们的光谱材料将非常适合这种分析。

The origin of massive stars (with masses over 10 solar masses) is one of the main unsolved problems in star formation and is currently the subject of heated debate. While the initial mass function of massive stars has long been recognised as an important topic, the binary properties of massive stars have been much less studied. However, it is becoming increasingly evident that only few massive stars appear to be single, and they may even have been part of binary systems that were dynamically dissolved. Understanding massive star formation is therefore equivalent to understanding massive binary formation. The companion star fraction for massive stars in the Orion Trapezium is 1.5, whereas it is 0.5 for low-mass stars in Orion. This discrepancy is a strong indicator that the formation of high-mass and low-mass binaries may be different, and that massive star formation is not likely to be merely a scaled-up version of lower-mass star formation. No less than four different hypotheses have been forwarded to explain the birth of massive binaries: (1) Fragmentation of massive disks around massive stars, (2) Bondi-Hoyle accretion onto a low-mass protobinary, (3) Encounters and tidal capture of intermediatemass protostars in a dense cluster, and (4) Dynamical three-body capture in a dense cluster. In order to test these theories, we need a more complete understanding of the binarity of massive stars at very young ages, when dynamical interactions have not yet been fully played out. We propose to embark on a systematic study of the approximately 80 massive stars in the Orion OB1 association, search for binaries, and determine their characteristics. This material can then be compared by theorists with their predictions of the four hypotheses for massive binary formation listed above. In addition we note that only preliminary atmospheric modelling has been made on a few of these OB stars and that our spectroscopic material will be ideally suited for such an analysis.