Astronomical Observatory, Warsaw University, Ujazdowskie 4, 00-478 Warsaw, Poland.
Enrico Fermi Institute, Department of Physics, Department of Astronomy and Astrophysics, and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637, USA.
Nature. 2016 Jun 23;534(7608):512-5. doi: 10.1038/nature18322.
The merger of two massive (about 30 solar masses) black holes has been detected in gravitational waves. This discovery validates recent predictions that massive binary black holes would constitute the first detection. Previous calculations, however, have not sampled the relevant binary-black-hole progenitors--massive, low-metallicity binary stars--with sufficient accuracy nor included sufficiently realistic physics to enable robust predictions to better than several orders of magnitude. Here we report high-precision numerical simulations of the formation of binary black holes via the evolution of isolated binary stars, providing a framework within which to interpret the first gravitational-wave source, GW150914, and to predict the properties of subsequent binary-black-hole gravitational-wave events. Our models imply that these events form in an environment in which the metallicity is less than ten per cent of solar metallicity, and involve stars with initial masses of 40-100 solar masses that interact through mass transfer and a common-envelope phase. These progenitor stars probably formed either about 2 billion years or, with a smaller probability, 11 billion years after the Big Bang. Most binary black holes form without supernova explosions, and their spins are nearly unchanged since birth, but do not have to be parallel. The classical field formation of binary black holes we propose, with low natal kicks (the velocity of the black hole at birth) and restricted common-envelope evolution, produces approximately 40 times more binary-black-holes mergers than do dynamical formation channels involving globular clusters; our predicted detection rate of these mergers is comparable to that from homogeneous evolution channels. Our calculations predict detections of about 1,000 black-hole mergers per year with total masses of 20-80 solar masses once second-generation ground-based gravitational-wave observatories reach full sensitivity.
两个巨大（约 30 个太阳质量）黑洞的合并已在引力波中被探测到。这一发现验证了最近的预测，即大质量双星黑洞将构成首次探测。然而，之前的计算没有足够准确地抽样相关的双星黑洞前身体——大质量、低金属丰度双星，也没有纳入足够真实的物理过程，无法进行优于几个数量级的稳健预测。在这里，我们报告了通过孤立双星演化形成双星黑洞的高精度数值模拟，为解释首个引力波源 GW150914 提供了一个框架，并对后续双星黑洞引力波事件的性质进行了预测。我们的模型表明，这些事件发生在金属丰度低于太阳金属丰度的十分之一的环境中，涉及初始质量为 40-100 个太阳质量的恒星，它们通过物质转移和共同包层阶段相互作用。这些前身星可能是在大爆炸后大约 20 亿年或更小的概率 110 亿年前形成的。大多数双星黑洞形成时没有超新星爆炸，它们的自转在出生后几乎没有变化，但不一定是平行的。我们提出的双星黑洞经典场形成，具有低的出生时速度（黑洞的速度）和受限的共同包层演化，产生的双星黑洞合并比涉及球状星团的动力学形成通道多约 40 倍；我们对这些合并的预测探测率与均匀演化通道相当。我们的计算预测，一旦第二代地面引力波观测站达到全灵敏度，每年将探测到约 1000 次总质量为 20-80 个太阳质量的黑洞合并。
