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arXiv 2307.13367astro-ph.GAastro-ph.COastro-ph.HEgr-qc
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LISA 大质量黑洞双星引力波的最小可测量偏心率

The minimum measurable eccentricity from gravitational waves of LISA massive black hole binaries

Mudit Garg, Shubhanshu Tiwari, Andrea Derdzinski, John G. Baker, Sylvain Marsat, Lucio Mayer

AI总结:

本研究针对红移z=1处的大质量黑洞双星,通过解析与贝叶斯推断数值方法,探究LISA的最小可测量偏心率阈值,明确其对红移后质量的强依赖性,为研究双星演化环境提供支撑。

摘要:

我们探究了红移 z=1 处、红移后黑洞质量 M_z 处于 10^{4.5}-10^{7.5} M_⊙ 范围的大质量黑洞双星(MBHBs)辐射的引力波的 LISA 偏心率测量阈值。偏心率可作为 MBHBs 演化至并合阶段所处环境的重要示踪物。为考虑 LISA 的运动并应用时间延迟干涉技术,我们采用 lisabeta 软件,并使用仅含旋近阶段的后牛顿模型 TaylorF2Ecc 生成时长为一年的偏心波形。我们通过计算匹配度与 Fisher 矩阵进行解析研究,同时通过改变内禀参数与外禀参数开展贝叶斯推断数值研究,以探究最小可测量偏心率(e_min,定义为并合前一年的偏心率)。我们发现 e_min 强烈依赖于 M_z,对质量比与外禀参数的依赖较弱。基于匹配度的信噪比判据表明,在 90% 置信度下,LISA 能够探测到较轻系统(M_z ≲ 10^{5.5} M_⊙)的 e_min ~ 10^{-2.5},以及较重 MBHBs 的 ~10^{-1.5}。在假设相对误差 <50% 的前提下,采用 Fisher 初始化与零噪声实现的贝叶斯推断将该下限推至较低质量双星的 e_min ~ 10^{-2.75}。对于 10^5 M_⊙ 的系统,贝叶斯推断能够恢复注入的 0.1 和 10^{-2.75} 偏心率,相对误差分别约为 10^{-2}% 和 ~10%。严格的贝叶斯赔率判据(ln{B}>8)给出了几乎一致的推断结果。对于我们关注的系统,解析与数值方法得出的结果几乎一致。LISA 将在十年内发射,这使得本研究对于揭示 MBHB 演化的奥秘具有重要价值与时效性。

英文摘要:

We explore the eccentricity measurement threshold of LISA for gravitational waves radiated by massive black hole binaries (MBHBs) with redshifted BH masses $M_z$ in the range $10^{4.5}$-$10^{7.5}~{\rm M}_\odot$ at redshift $z=1$. The eccentricity can be an important tracer of the environment where MBHBs evolve to reach the merger phase. To consider LISA's motion and apply the time delay interferometry, we employ the lisabeta software and produce year-long eccentric waveforms using the inspiral-only post-Newtonian model TaylorF2Ecc. We study the minimum measurable eccentricity ($e_{\rm min}$, defined one year before the merger) analytically by computing matches and Fisher matrices, and numerically via Bayesian inference by varying both intrinsic and extrinsic parameters. We find that $e_{\rm min}$ strongly depends on $M_z$ and weakly on mass ratio and extrinsic parameters. Match-based signal-to-noise ratio criterion suggest that LISA will be able to detect $e_{\rm min}\sim10^{-2.5}$ for lighter systems ($M_z\lesssim10^{5.5}~{\rm M}_\odot$) and $\sim10^{-1.5}$ for heavier MBHBs with a $90$ per cent confidence. Bayesian inference with Fisher initialization and a zero noise realization pushes this limit to $e_{\rm min}\sim10^{-2.75}$ for lower-mass binaries, assuming a $<50$ per cent relative error. Bayesian inference can recover injected eccentricities of $0.1$ and $10^{-2.75}$ for a $10^5~{\rm M}_\odot$ system with a $\sim10^{-2}$ per cent and a $\sim10$ per cent relative errors, respectively. Stringent Bayesian odds criterion ($\ln{B}>8$) provides nearly the same inference. Both analytical and numerical methodologies provide almost consistent results for our systems of interest. LISA will launch in a decade, making this study valuable and timely for unlocking the mysteries of the MBHB evolution.

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