标题： 关于合并双中子星形成的黑洞：它能以多快的速度自转？ 显示英文标题

标题： On the black hole from merging binary neutron stars: how fast can it spin?

摘要： 中子星的合并通常会导致一个围绕黑洞的环状结构形成，其旋转能量可以被利用来潜在地驱动短时伽马射线暴。 我们研究了自旋与轨道角动量对齐的等质量双星合并，以确定黑洞可能达到的最大自旋。 我们的初始数据是无旋转的双星系统，我们向其中添加不同量的旋转以增加总角动量。 尽管初始数据违反了约束方程，但使用约束阻尼的CCZ4公式得到了比无旋转初始数据和标准公式更小的违反情况。 有趣的是，我们发现存在一个无量纲自旋的上限$J/M^2 \simeq 0.89$，并且任何额外给予双星系统的角动量最终都会进入环状结构而不是黑洞，从而提供了另一个支持宇宙审查假说的非平凡例子。 显示英文摘要

摘要： The merger of two neutron stars will in general lead to the formation of a torus surrounding a black hole whose rotational energy can be tapped to potentially power a short gamma-ray burst. We have studied the merger of equal-mass binaries with spins aligned with the orbital angular momentum to determine the maximum spin the black hole can reach. Our initial data consists of irrotational binaries to which we add various amounts of rotation to increase the total angular momentum. Although the initial data violates the constraint equations, the use of the constraint-damping CCZ4 formulation yields evolutions with violations smaller than those with irrotational initial data and standard formulations. Interestingly, we find that a limit of $J/M^2 \simeq 0.89$ exists for the dimensionless spin and that any additional angular momentum given to the binary ends up in the torus rather than in the black hole, thus providing another nontrivial example supporting the cosmic censorship hypothesis.