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arXiv 2304.04800gr-qcastro-ph.CO
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利用天琴(TianQin)探测引力波的强引力透镜效应

Detecting Strong Gravitational Lensing of Gravitational Waves with TianQin

Xin-yi Lin, Jian-dong Zhang, Liang Dai, Shun-Jia Huang, Jianwei Mei

AI总结:

本文针对天琴空间引力波探测器,研究其探测受强引力透镜作用的大质量黑洞并合信号的能力,考虑三种透镜模型并结合衍射效应计算波形,通过Fisher分析得出透镜参数估计精度,明确透镜效应提升源参数估计精度的主导因素是信噪比增加。

摘要:

当引力波(GWs)在传播至地球的途中经过大质量天体时,会产生强引力透镜效应。此时引力波信号会被放大、偏折,且出现时间延迟。通过分析受透镜作用的引力波波形,可推断透镜的物理性质。另一方面,若在引力波数据分析中忽略透镜效应,可能会在源参数估计中引入系统误差。\n作为空间引力波探测器,天琴(TianQin)计划于21世纪30年代发射。它预计可探测到红移z=15处的数十个大质量黑洞并合(MBHBs)事件,因此在任务寿命期内有很高概率探测到至少一起引力透镜事件。本文探讨了天琴探测受透镜作用的大质量黑洞并合信号的能力。\n本研究考虑了三种透镜模型:点质量模型、奇异等温球(SIS)模型和纳瓦罗-弗伦克-怀特(NFW)模型。空间引力波探测器的敏感频段约为毫赫兹,对应的引力波波长可与透镜的引力长度尺度相当,因此需要考虑波的衍射效应。在计算受透镜作用的波形时,我们在高频段采用几何光学近似以加快计算速度,在低频段则精确计算衍射积分。\n通过Fisher分析,我们研究了透镜参数的估计精度。结果显示,点质量透镜和SIS透镜的质量估计精度可达10^-3量级,NFW透镜的密度估计精度可达10^-5量级。我们还评估了透镜效应对源参数估计精度的影响,发现精度提升主要由信噪比的提高主导。

英文摘要:

When gravitational waves (GWs) pass by a massive object on its way to Earth, a strong gravitational lensing effect will happen. Thus, the GW signal will be amplified, deflected, and delayed in time. Through analyzing the lensed GW waveform, physical properties of the lens can be inferred. On the other hand, neglecting lensing effects in the analysis of GW data may induce systematic errors in the estimating of source parameters. As a space-borne GW detector, TianQin will be launched in the 2030s. It is expected to detect dozens of mergers of massive black hole binaries (MBHBs) as far as z=15 and thus will have high probability to detect at least one lensed event during the mission lifetime. In this article, we discuss the capability of TianQin to detect lensed MBHB signals.Three lens models are considered in this work: the point mass model, the singular isothermal sphere (SIS) model, and the Navarro-Frenk-White (NFW) model. The sensitive frequency band for space-borne GW detectors is around millihertz, and the corresponding GW wavelength could be comparable to the lens gravitational length scale, which requires us to account for wave diffraction effects. In calculating lensed waveforms, we adopt the approximation of geometric optics at high frequencies to accelerate computation, while precisely evaluating the diffraction integral at low frequencies. Through a Fisher analysis, we analyze the accuracy to estimate the lens parameters. We find that the accuracy can reach to the level of 10^-3 for the mass of point mass and SIS lens and to the level of 10^-5 for the density of the NFW lens. We also assess the impact on the accuracy of estimating the source parameters and find that the improvement of the accuracy is dominated by the increasing of signal-to-noise ratio.

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