并非所有在星团中形成的黑洞双星的自旋都是各向同性的，也并非所有在孤立环境中形成的黑洞双星的自旋都是对齐的
Not all spins of black-hole binaries formed in clusters are isotropic and not all spins of black-hole binaries formed in isolation are aligned
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中文总结 AI 辅助
本文挑战了黑洞双星形成通道的自旋方向标准预期，提出了解析模型描述星团动力学形成与孤立形成的自旋分布，并考虑了并合后随机化及超新星踢速度的影响。
中文摘要 AI 辅助
自旋方向是区分通过引力波观测到的并合恒星质量双黑洞形成通道的有前景的观测量。在这项工作中，我们挑战了标准预期，即通过星团中动力学相互作用形成的双星具有各向同性分布的自旋，而孤立形成的双星的自旋与轨道角动量对齐。对于动力学形成的双星，我们考虑了观测发现，即星团中恒星的自旋可能表现出一定程度的优先对齐，并构建了由此产生的黑洞自旋方向的简单几何描述。这导致了第一代黑洞双星极角的解析联合分布，其关键特征是双星的两个自旋-轨道倾角之间存在相关性。我们表明，在合理假设下，且与初始自旋构型无关，单次黑洞并合后自旋完全随机化，这意味着通过层级并合形成的双星具有各向同性分布的自旋取向。对于孤立双星，我们引入了一个简单的模型，描述自旋作为第一次超新星爆发期间产生的原生踢速度的函数演化，同时考虑了潮汐相互作用和质量比反转。所得分布也是完全解析的。我们研究了相对论性自旋进动以及星团有限逃逸速度对我们几何推导的分布的影响。我们的结果为在引力波群体拟合中建模并合黑洞的自旋方向提供了一个简单的解析框架。
英文摘要
Spin directions are promising observables for distinguishing between the formation channels of merging stellar-mass binary black holes with gravitational-wave observations. In this work, we challenge the standard expectation that binaries formed via dynamical interactions in stellar clusters have isotropically distributed spins and that binaries formed in isolation have spins aligned with the orbital angular momentum. For dynamically formed binaries, we account for observational findings suggesting that the spins of stars in clusters may exhibit a preferred degree of alignment and construct a simple geometrical description of the resulting black-hole spin directions. This results in an analytical joint distribution for the polar angles of first-generation black-hole binaries, whose key feature is a correlation between the two spin-orbit tilts. We show that, under reasonable assumptions and independently of the initial spin configuration, spins are fully randomized after a single black-hole merger, implying that binaries formed through hierarchical mergers have isotropically distributed spin orientations. For isolated binaries, we introduce a simple model for spin evolution as a function of the natal kick imparted during the first supernova explosion, while accounting for tidal interactions and mass-ratio reversal. The resulting distribution is also fully analytic. We investigate the impact of relativistic spin precession, as well as that of the finite escape speed of clusters, on our geometrically derived distributions. Our results provide a simple analytical framework for modeling the spin directions of merging black holes in gravitational-wave population fits.
发表机构
- Universitá degli Studi di Milano-Bicocca（米兰比可卡大学）
- INFN, Sezione di Milano-Bicocca（意大利国家核物理研究所米兰-比可卡分部）
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