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arXiv 2607.08445gr-qcastro-ph.IMhep-ph
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激光干涉空间天线(LISA)的信噪比等高线

Signal-to-Noise Ratio Contours for LISA

Institute for Theoretical Physics, University of Münster(明斯特大学理论物理研究所);Kavli IPMU (WPI), UTIAS, The University of Tokyo(东京大学 Kavli宇宙起源与演化研究前沿中心(UTIAS));Department of Physics and Astronomy, UT Rio Grande Valley(里奥格兰德河谷大学物理与天文学系)

Kai Schmitz, Joseph D. Romano

AI总结:

研究LISA对随机引力波背景信号灵敏度问题,首次推导任意信号强度下LISA自相关测量最优信噪比表达式,得出相关数值结论并通过灵敏度曲线说明,为评估LISA数据信噪比提供新依据。

摘要:

激光干涉空间天线(LISA)将在毫赫兹频率下搜索来自天体物理和宇宙学源的随机引力波(GW)背景,从而开启GW天文学的新篇章。在文献中,LISA对预期GW背景(GWB)信号的灵敏度通常根据假设完全了解探测器噪声的预期信噪比(SNR)来量化。然而,常用的SNR表达式仅在弱GWB信号的极限下有效,这使得文献中报道的大量SNR值不准确。在本文中,我们首次推导了LISA自相关测量的预期最优SNR的表达式,该表达式在任意信号强度下均有效。基于我们的广义表达式,我们得出结论,在从f_min到f_max的频带上,观测时间为T_obs的LISA数据产生的SNR永远不会超过SNR_max = sqrt(T_obs(f_max - f_min)),对于典型任务参数,该值约为SNR_max <~ 10^4。我们在不同SNR水平的广义幂律积分(PLI)灵敏度曲线上说明了我们的发现,即在GW能量密度功率谱图中的LISA SNR等高线。与早期关于PLI灵敏度曲线的工作相比,我们特别发现LISA SNR等高线有一个上限,大约是LISA应变噪声曲线乘以欧拉数e。对于不比这个范围弱太多的GWB信号,LISA自相关测量的预期SNR需要根据我们的新表达式进行评估。我们关于LISA SNR等高线的数值结果可在Zenodo上获取。

英文摘要:

The Laser Interferometer Space Antenna (LISA) will search for a stochastic gravitational-wave (GW) background at millihertz frequencies, from both astrophysical and cosmological sources, and thereby open a new chapter in GW astronomy. In the literature, LISA's sensitivity to prospective GW background (GWB) signals is often quantified in terms of an expected signal-to-noise ratio (SNR) assuming perfect knowledge of the detector noise. The commonly employed expression for the SNR is, however, valid only in the limit of a weak GWB signal, which renders a large number of SNR values reported in the literature inaccurate. In this paper, we address this issue by deriving for the first time an expression for the expected optimal SNR of a LISA auto-correlation measurement that is valid at arbitrary signal strength. Based on our generalized expression, we conclude that LISA data worth an observing time of T_obs across the frequency band from f_min to f_max will never yield an SNR in excess of SNR_max = sqrt(T_obs(f_max-f_min)), which evaluates to SNR_max <~ 10^4 for typical mission parameters. We illustrate our findings in terms of generalized power-law-integrated (PLI) sensitivity curves at different SNR levels, i.e., LISA SNR contour lines in plots of the GW energy-density power spectrum. In contrast to earlier work on PLI sensitivity curves, we notably find that the LISA SNR contours are bounded from above, approximately by the LISA strain noise curve multiplied by a factor of Euler's number e. For GWB signals not much weaker than this range, the expected SNR for a LISA auto-correlation measurement needs to be evaluated based on our new expression. Our numerical results for the LISA SNR contours are available on Zenodo [https://doi.org/10.5281/zenodo.21275527].

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