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arXiv 2006.14587astro-ph.HEastro-ph.GA
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年轻大质量疏散星团的LISA源

LISA sources from young massive and open stellar clusters

Sambaran Banerjee

摘要:

我研究的潜在作用,年轻的大质量(YMCs)和疏散星团(OC)在组装恒星质量的双黑洞(BBHs),这将是可检测的持续引力波(GW)源即将到来的LISA任务。星团内部的高能动力学相互作用使它们成为组装BBH和其他类型的双紧双星的工厂,这些双星经历广义相对论(GR)螺旋和合并。这种吸气的初始阶段通常会扫过LISA GW带。在这里,这样的LISA源研究从一组星团的演化模型,质量范围超过$10^4M_\odot-10^5M_\odot$,代表YMCs和中老年OC在富金属和贫金属的环境中的本地宇宙。这些模型是通过长期的、直接的、相对论性的多体计算发展起来的,这些计算结合了最先进的恒星演化和残余物形成模型。基于这样的模型集群构建的本地宇宙的模型,它表明,YMC和中年龄的OC将产生几十到几百秒的LISA BBH源在当前的宇宙纪元与GW的频率在$10^{-3}{\rm~Hz} - 10^{-1}{\rm~Hz}$和信号/噪声比(S/N)$>5$,假设任务寿命为5或10年。这种LISA BBH在总质量上具有双峰分布,通常是偏心的($\lesssim0.7$),并且通常具有相似的组分质量,尽管质量不对称的系统是可能的。实际上,今天将有1000个来自YMC和OC的LISA可检测的BBH。这样,YMC和OC将为LISA可探测到的恒星质量BBH群体提供重要和主要的贡献。这些BBH中的一小部分,$<5$ %,将在任务时间跨度内经历GR螺旋上升,使其进入LIGO-Virgo GW频段并合并; $<15$ %将在两倍的时间跨度内完成。

英文摘要:

I study the potential role of young massive (YMCs) and open star clusters (OCs) in assembling stellar-mass binary black holes (BBHs) which would be detectable as persistent gravitational-wave (GW) sources by the forthcoming LISA mission. The energetic dynamical interactions inside star clusters make them factories of assembling BBHs and other types of double-compact binaries that undergo general-relativistic (GR) inspiral and merger. The initial phase of such inspirals would, typically, sweep through the LISA GW band. Here, such LISA sources are studied from a set of evolutionary models of star clusters with masses ranging over $10^4M_\odot-10^5M_\odot$ that represent YMCs and intermediate-aged OCs in metal-rich and metal-poor environments of the Local Universe. These models are evolved with long-term, direct, relativistic many-body computations incorporating state-of-the-art stellar-evolutionary and remnant-formation models. Based on models of Local Universe constructed with such model clusters, it is shown that YMCs and intermediate-aged OCs would yield several 10s to 100s of LISA BBH sources at the current cosmic epoch with GW frequency within $10^{-3}{\rm~Hz} - 10^{-1}{\rm~Hz}$ and signal-to-noise-ratio (S/N) $>5$, assuming a mission lifetime of 5 or 10 years. Such LISA BBHs would have a bimodal distribution in total mass, be generally eccentric ($\lesssim0.7$), and typically have similar component masses although mass-asymmetric systems are possible. Intrinsically, there would be 1000s of present-day, LISA-detectable BBHs from YMCs and OCs. That way, YMCs and OCs would provide a significant and the dominant contribution to the stellar-mass BBH population detectable by LISA. A small fraction, $<5$%, of these BBHs would undergo GR inspiral to make it to LIGO-Virgo GW frequency band and merge, within the mission timespan; $<15$% would do so within twice the timespan.

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