与中等质量黑洞相遇的偏心白矮双星系统的演化与并合
Evolution and mergers of eccentric white dwarf binaries encountering intermediate-mass black holes
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中文总结 AI 辅助
本研究通过三维流体动力学模拟，发现中等质量黑洞的近距离相遇能显著加速偏心白矮双星系统的并合，并影响其并合结果与角动量演化，从而定量改变此类双星系统的演化路径。
中文摘要 AI 辅助
我们研究了近距离掠过中等质量黑洞（IMBH）如何改变具有标称洛希瓣溢出的偏心白矮星（WD）双星系统的演化，该溢出发生在内部近心点处。利用三维光滑粒子流体动力学方法，我们追踪了偏心率为$e_{\rm in}=0.6$、质量比为$q=0.2$--$0.7$的双星系统，它们围绕一个史瓦西中等质量黑洞沿抛物线、逆行轨道运动，并考虑了两种相遇强度，$\beta^b=0.5$和$1.5$。我们将这些系统与在孤立环境中演化的相同双星系统进行了比较。中等质量黑洞极大地加速了并合过程。每个受中等质量黑洞扰动的双星系统，若发生并合，则在其第二次内部近心点通过期间或之后不久即完成并合，该时间总是短于孤立环境下的并合时间。并合结果与相遇强度并非单调相关。$q=0.2$的双星系统在$\beta^b=1.5$时保留了两个束缚核，但在$\beta^b=0.5$时发生并合。在更深的相遇中，该系统稳定在了一个偏心率较低的相遇后轨道上，这表明相遇相对于内部轨道的时机起着重要作用。深度相遇还会在$q=0.2$--$0.4$的情况下产生内部轨道角动量的瞬态反转，而束缚在吸积体上的物质比束缚在供体上的物质获得更多的自旋角动量。双星系统质心围绕中等质量黑洞的比轨道角动量仅改变了其初始值的几个$\times10^{-4}$。我们还识别出了氦起源物质，这些物质可以在动力学时标上燃烧氦，对于$q=0.7$的情况，其量约为氦起源质量的$\sim15$--$17\\%$。因此，中等质量黑洞的相遇可以定量地改变偏心白矮双星系统的演化。
英文摘要
We study how a close passage past an intermediate-mass black hole (IMBH) changes the evolution of an eccentric white dwarf (WD) binary that has nominal Roche lobe overflow at internal pericenter. Using three-dimensional smoothed particle hydrodynamics, we follow binaries with eccentricity $e_{\rm in}=0.6$ and mass ratios $q=0.2$ -- $0.7$ on parabolic, retrograde orbits around a Schwarzschild IMBH at two encounter strengths, $β^b=0.5$ and $1.5$. We compare them with the same binaries evolved in isolation. The IMBH greatly speeds up the merger. Every IMBH-perturbed binary that merges does so during or shortly after its second internal pericenter passage, which is always less than the time taken to merge in isolation. The merger outcome is not monotonic with encounter strength. The $q=0.2$ binary retains two bound cores for $β^b=1.5$ but merges at $β^b=0.5$. In the deeper encounter it settles onto a less eccentric post-encounter orbit, showing that the timing of the encounter relative to the inner orbit plays an important role. Deep encounters also produce transient reversals of the internal orbital angular momentum for $q=0.2$ -- $0.4$, while the material bound to the accretor gains more spin angular momentum than that bound to the donor. The specific orbital angular momentum of the binary CM around the IMBH changes by only a few $\times10^{-4}$ of its initial value. We also identify He-origin material that can burn helium on a dynamical timescale, amounting to $\sim15$ -- $17\%$ of the He-origin mass for $q=0.7$. IMBH encounters can therefore quantitatively change the evolution of eccentric WD binaries.
发表机构
- Indian Institute of Technology Kanpur（坎普尔印度理工学院）
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