论文标题
从最负$χ_\ mathrm {eff} $ systems限制层次黑洞合并。
Limits on hierarchical black hole mergers from the most negative $χ_\mathrm{eff}$ systems
论文作者
论文摘要
有人提出，二进制黑洞（BBH）系统中的一些黑洞（BHS）是从“等级合并”（HM）诞生的；即较小的BHS的早期合并。这些HM产品具有自旋幅度$χ\ sim 0.7 $，并且，如果将它们动态组装到BBH系统中，则有时会与二进制轨道角动量进行抗对齐。实际上，如Baibhav等人。 （2020）表明，包括HM产品在内的BBH系统的$ \ sim16 \％$将具有有效的Inspiral旋转参数，$χ_\ Mathrm {eff} <-0.3 $。然而，Ligo-Virgo-Kagra（LVK）重力波（GW）探测器尚未观察到具有$χ_\ MathRM {eff} \ Lesssim -0.2 $的BBH系统，导致人群中HM产品的上限。我们符合BBH系统的天体物理质量和自旋分布，并测量具有$χ_\ Mathrm {eff} <-0.3 $的BBH系统的分数，这意味着对HM分数的上限。我们发现，在基础BBH人群中，不到$ 26 \％的系统包括HM产品（90 \％。信誉）。即使在具有初级质量的BBH系统中，$ m_1 = 60 \，m_ \ odot $，HM分数小于69 \％，这可能会限制配对稳定质量间隙的位置。如果我们无法观察到具有$χ_\ Mathrm {eff} <-0.3 $的BBH，则有300个GW事件（可以在LVK的下一次观察跑中进行预期），我们可以得出结论，HM分数小于$ 2.5^{+9.1} _ { - 2.2} _ { - 2.2} _ { - 2.2} \％$ $。
It has been proposed that some black holes (BHs) in binary black hole (BBH) systems are born from "hierarchical mergers" (HM); i.e. earlier mergers of smaller BHs. These HM products have spin magnitudes $χ\sim 0.7$, and, if they are dynamically assembled into BBH systems, their spin orientations will be sometimes anti-aligned with the binary orbital angular momentum. In fact, as Baibhav et al. (2020) showed, $\sim16\%$ of BBH systems that include HM products will have an effective inspiral spin parameter, $χ_\mathrm{eff} < -0.3$. Nevertheless, the LIGO-Virgo-Kagra (LVK) gravitational-wave (GW) detectors have yet to observe a BBH system with $χ_\mathrm{eff} \lesssim -0.2$, leading to upper limits on the fraction of HM products in the population. We fit the astrophysical mass and spin distribution of BBH systems and measure the fraction of BBH systems with $χ_\mathrm{eff} < -0.3$, which implies an upper limit on the HM fraction. We find that fewer than $26\%$ of systems in the underlying BBH population include HM products (90\%. credibility). Even among BBH systems with primary masses $m_1=60\,M_\odot$, the HM fraction is less than 69\%, which may constrain the location of the pair-instability mass gap. With 300 GW events (to be expected in the LVK's next observing run), if we fail to observe a BBH with $χ_\mathrm{eff} < -0.3$, we can conclude that the HM fraction is smaller than $2.5^{+9.1}_{-2.2}\%$.
