Birmingham Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA.
Nature. 2017 Aug 23;548(7667):426-429. doi: 10.1038/nature23453.
The direct detection of gravitational waves from merging binary black holes opens up a window into the environments in which binary black holes form. One signature of such environments is the angular distribution of the black hole spins. Binary systems that formed through dynamical interactions between already-compact objects are expected to have isotropic spin orientations (that is, the spins of the black holes are randomly oriented with respect to the orbit of the binary system), whereas those that formed from pairs of stars born together are more likely to have spins that are preferentially aligned with the orbit. The best-measured combination of spin parameters for each of the four likely binary black hole detections GW150914, LVT151012, GW151226 and GW170104 is the 'effective' spin. Here we report that, if the magnitudes of the black hole spins are allowed to extend to high values, the effective spins for these systems indicate a 0.015 odds ratio against an aligned angular distribution compared to an isotropic one. When considering the effect of ten additional detections, this odds ratio decreases to 2.9 × 10 against alignment. The existing preference for either an isotropic spin distribution or low spin magnitudes for the observed systems will be confirmed (or overturned) confidently in the near future.
从合并的双黑洞直接探测引力波为我们提供了一个了解双黑洞形成环境的窗口。这种环境的一个特征是黑洞自旋的角分布。通过已经紧凑的物体之间的动力学相互作用形成的双星系统预计具有各向同性的自旋方向（即黑洞的自旋相对于双星系统的轨道随机定向），而那些由一对恒星形成的双星系统更有可能具有优先与轨道对齐的自旋。对于 GW150914、LVT151012、GW151226 和 GW170104 这四个可能的双黑洞探测中每个系统的自旋参数的最佳测量组合是“有效”自旋。在这里，我们报告说，如果黑洞自旋的大小允许扩展到高值，那么与各向同性相比，这些系统的有效自旋表明与对齐的角分布相比，其比值为 0.015。当考虑到另外十个探测的影响时，这种比值下降到 2.9×10 反对齐。在不久的将来，我们将有信心确认（或推翻）现有系统中对各向同性自旋分布或低自旋大小的偏好。
