发表机构
Tsung-Dao Lee Institute, Shanghai Jiao-Tong University; Center for Astrophysics and Planetary Science, Department of Astronomy, Cornell University; Institute for Astronomy, School of Physics, Zhejiang University; Center for Cosmology and Computational Astrophysics, Institute for Advanced Study in Physics, Zhejiang University（李政道研究所，上海交通大学; 康奈尔大学天文学系天文与行星科学中心; 浙江大学物理学院天体物理研究所; 浙江大学物理高等研究院宇宙学与计算天体物理中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究探讨孤立双星演化能否产生高自旋主黑洞的不等质量双黑洞并合，提出两种可行路径，指出等级并合并非唯一起源，未来可通过探测自旋约0.7的事件区分两种起源。
AI 中文摘要
GWTC-5已发现一个双黑洞并合（BBH）子群，其主黑洞（BH）自旋较高，且可能具有不等质量。GW241110还表现出较大的自旋-轨道错位，这表明其起源于等级并合。然而，其他形成场景也有可能甚至很可能存在，尤其是对于那些自旋-轨道错位无约束的事件。作为等级并合的替代方案，我们研究双星演化是否能产生具有高自旋主黑洞的不等质量BBH并合。我们没有进行全面的种群合成计算，而是考察形成并合BBH的演化路径并评估其不确定性。我们确定了两种产生具有高自旋主黑洞的不等质量BBH的可能路径：在初始宽双星中，质量比反转可使潮汐自旋加速的次生成黑洞比初生成黑洞质量更大且旋转更快；或者在初始密的不等质量双星中，主星可发生化学均匀演化，而次星正常演化，产生比伴星质量更大的高自旋初生成黑洞。通常，较大的自旋-轨道错位可由较大的 natal kick（ natal 反冲）或伴星诱导的节点进动和/或Zeipel-Lidov-Kozai振荡产生。我们得出结论，产生具有高自旋主黑洞的不等质量BBH并不唯一需要等级并合，尽管每条孤立双星路径都面临重要的理论约束。未来对更多主黑洞自旋约为0.7的并合事件的探测，将区分双星演化和等级并合起源。
英文摘要
GWTC-5 has revealed a subpopulation of merging binary black holes (BBHs) with a high-spin primary black hole (BH) and possibly unequal BH masses. GW241110 additionally exhibits a large spin-orbit misalignment, which suggests a hierarchical-merger origin. However, other formation scenarios are possible or even likely, especially for events without constraints on spin-orbit misalignment. As an alternative to hierarchical mergers, we investigate whether binary evolution can produce unequal-mass BBH mergers with a high-spin primary BH. Rather than performing comprehensive population-synthesis calculations, we examine the evolutionary pathways of forming merging BBHs and assess their uncertainties. We identify two possible pathways for producing unequal-mass BBHs with a high-spin primary. In initially wide binaries, mass-ratio reversal can make the tidally spun-up second-born BH both more massive and more rapidly rotating than the first-born BH; alternatively, in an initially close, unequal-mass binary, the primary star may evolve chemically homogeneously, while the secondary star evolves normally, producing a high-spin first-born BH that is more massive than its companion. Generally, large spin-orbit misalignment can be produced by large natal kicks or tertiary-induced nodal precession and/or Zeipel-Lidov-Kozai oscillations. We conclude that hierarchical mergers are not uniquely required to produce unequal-mass BBHs with a high-spin primary BH, although each isolated-binary pathway faces important theoretical constraints. Future detections of more merger events with primary BH spins around 0.7 would discriminate between binary evolution and hierarchical merger origin.
Commentssubmitted
