Center for Relativistic Astrophysics and School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, VIC 3800, Australia.
Phys Rev Lett. 2018 Nov 9;121(19):191102. doi: 10.1103/PhysRevLett.121.191102.
Coalescing binary black holes emit anisotropic gravitational radiation. This causes a net emission of linear momentum that produces a gradual acceleration of the source. As a result, the final remnant black hole acquires a characteristic velocity known as recoil velocity or gravitational kick. The symmetries of gravitational wave emission are reflected in the interactions of the gravitational wave modes emitted by the binary. In this Letter, we make use of the rich information encoded in the higher-order modes of the gravitational wave emission to infer the component of the kick along the line of sight (or radial kick). We do this by performing parameter inference on simulated signals given by numerical relativity waveforms for nonspinning binaries using numerical relativity templates of aligned-spin (nonprecessing) binary black holes. We find that for suitable sources, namely those with mass ratio q≥2 and total mass M∼100 M_{⊙}, and for modest radial kicks of 120 km/s, the 90% credible intervals of our posterior probability distributions can exclude a zero kick at a signal-to-noise ratio of 15, using a single Advanced LIGO detector working at its early sensitivity. The measurement of a nonzero radial kick component would provide the first observational signature of net transport of linear momentum by gravitational waves away from their source.
双黑洞并合会辐射各向异性的引力波。这种辐射会导致线性动量的净发射，从而使源逐渐加速。结果，最终剩余的黑洞会获得一种特征速度，称为反冲速度或引力踢。引力波发射的对称性反映在双黑洞所发射的引力波模式的相互作用中。在本 Letter 中，我们利用引力波发射的高阶模式中所编码的丰富信息，来推断沿视线方向（或径向踢）的踢分量。我们通过对数值相对论模拟信号进行参数推断来实现这一点，这些模拟信号是基于非旋转双星的数值相对论波形，并使用对准自旋（非进动）双星黑洞的数值相对论模板。我们发现，对于合适的源，即那些质量比 q≥2 和总质量 M∼100 M_{⊙}的源，以及适度的径向踢 120 km/s，使用单个处于早期灵敏度的先进 LIGO 探测器，在信噪比为 15 的情况下，我们后验概率分布的 90%置信区间可以排除零踢。测量到非零径向踢分量将提供线性动量通过引力波从源向外净传输的第一个观测特征。
