Phase effects from strong gravitational lensing of gravitational waves
Phase effects from strong gravitational lensing of gravitational waves
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DOI：
10.1103/physrevd.103.064047
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发表时间：
2020-08
影响因子：
5
通讯作者：
J. Ezquiaga;D. Holz;Wayne Hu;Macarena Lagos;R. Wald
中科院分区：
文献类型：
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作者：
J. Ezquiaga;D. Holz;Wayne Hu;Macarena Lagos;R. Wald
评估两个或更多引力波(GW)事件是同一震源的透镜图像的概率需要了解透镜图像的特性。对于足够短的波长，可以忽略波的影响，透镜成像通常具有固定的相对相移，这在透镜假设中需要考虑。对于由四极辐射主导的非进动圆形双星，这些透镜相移是简并的，要么是合并相或探测器的移位，要么是取向角随倾角的移位。这种简并被高次简并模的存在所打破，高次简并模在前者中为$|m|\ne 2$，在后者中为$|m|\ne L$。进动或偏心的存在也将打破这种简并。这意味着透镜的GW图像不一定与广义相对论(GR)的预测一致(非透镜的)。因此，与传统的电磁波场景不同，GWS的强透镜可以产生可以观察到的具有修正的相位演化的图像。然而，我们发现取向角移动的模板仍然是一个很好的近似值，当质量比达到1/18时，信噪比差小于1美元，当进动参数达到0.5和偏心率达到0.4时，信噪比差异小于5美元。我们的结论是，最优的强透镜搜索策略将在强透镜识别的所有阶段结合相位信息，并在最终评估多个透镜事件的概率时进行精确处理。这项工作阐明了强透镜在GWS相位演化中的作用：它如何导致GR的明显偏差，它如何影响GW事件的可探测性，以及如何利用它来帮助识别引力波源强引力透镜的情况。
Assessing the probability that two or more gravitational wave (GW) events are lensed images of the same source requires an understanding of the properties of the lensed images. For short enough wavelengths where wave effects can be neglected, lensed images will generically have a fixed relative phase shift that needs to be taken into account in the lensing hypothesis. For non-precessing, circular binaries dominated by quadrupole radiation these lensing phase shifts are degenerate with either a shift in the coalescence phase or a detector and inclination dependent shift in the orientation angle. This degeneracy is broken by the presence of higher harmonic modes with $|m|\ne 2$ in the former and $|m| \ne l$ in the latter. The presence of precession or eccentricity will also break this degeneracy. This implies that a lensed GW image will not necessarily be consistent with (unlensed) predictions from general relativity (GR). Therefore, unlike the conventional scenario of electromagnetic waves, strong lensing of GWs can lead to images with a modified phase evolution that can be observed. However, we find that templates with a shifted orientation angle remain a good approximation, with signal-to-noise ratio differences of less than $1\%$ for mass ratios up to 1/18, and less than $5\%$ for precession parameters up to 0.5 and eccentricities up to 0.4. We conclude that an optimal strong lensing search strategy would incorporate phase information in all stages of the identification of strong-lensing, with an exact treatment in the final assessment of the probability of multiple lensed events. This work clarifies the role that strong lensing plays in the phase evolution of GWs: how it can lead to apparent deviations from GR, how it can affect the detectability of GW events, and how it can be exploited to help identify cases of strong gravitational lensing of gravitational wave sources.