标题： 进动黑洞双星中的角动量去向 显示英文标题

标题： Where angular momentum goes in a precessing black hole binary

摘要： 我们演化一组32个质量相等的黑洞双星，其自旋共线（自旋大小为$|\vec{S}_{1,2}/m^2_{1,2}|=0.8$），以研究在高度非线性下落和合并区域中的进动效应。 我们将瞬时辐射角动量的方向，$\hat{\delta J}_{\rm rad}(t)$，与总角动量的方向，$\hat{J}(t)$，以及轨道角动量，$\hat{L}(t)$，进行比较。 我们发现$\hat{\delta J}_{\rm rad}(t)$在整个演化过程中大致遵循$\hat{L}$。 在轨道演化和并合过程中，我们观察到$\vec{L}$与总自旋$\vec{S}$之间的角度大致保持不变，误差在$1^\circ$范围内，这使我们能够提出并检验关于并合残余质量与自旋的模型。 例如，我们验证了\hangup 效应是主要效应，并基本解释了这些进动系统所辐射的总能量和角动量。 我们还验证了总角动量在 inspiral 过程中显著减小，其方向变化小于$\sim 5^\circ$。 $\vec J$方向的最大变化发生在自旋几乎与轨道角动量反向对齐时。 根据我们的结果，我们推测过渡性进动，这会导致$\vec J$方向的大幅变化，在质量相近的双星系统中是不可能的，并且需要质量比$m_1/m_2\lesssim1/4$。 显示英文摘要

摘要： We evolve a set of 32 equal-mass black-hole binaries with collinear spins (with intrinsic spin magnitudes $|\vec{S}_{1,2}/m^2_{1,2}|=0.8$) to study the effects of precession in the highly nonlinear plunge and merger regimes. We compare the direction of the instantaneous radiated angular momentum, $\hat{\delta J}_{\rm rad}(t)$, to the directions of the total angular momentum, $\hat{J}(t)$, and the orbital angular momentum, $\hat{L}(t)$. We find that $\hat{\delta J}_{\rm rad}(t)$ approximately follows $\hat{L}$ throughout the evolution. During the orbital evolution and merger, we observe that the angle between $\vec{L}$ and total spin $\vec{S}$ is approximately conserved to within $1^\circ$, which allows us to propose and test models for the merger remnant's mass and spin. For instance, we verify that the \hangup effect is the dominant effect and largely explains the observed total energy and angular momentum radiated by these precessing systems. We also verify that the total angular momentum, which significantly decreases in magnitude during the inspiral, varies in direction by less than $\sim 5^\circ$. The maximum variation in the direction of $\vec J$ occurs when the spins are nearly antialigned with the orbital angular momentum. Based on our results, we conjecture that transitional precession, which would lead to large variations in the direction of $\vec J$, is not possible for similar-mass binaries and would require a mass ratio $m_1/m_2\lesssim1/4$.