McMillan SL
Astrophys J. 2000 Jan 1;528(1):L17-L20. doi: 10.1086/312422.
Mergers of black hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates that are too low to be of observational interest. In this Letter, we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation then causes them to sink to the cluster core, where they form binaries. These black hole binaries become more tightly bound by superelastic encounters with other cluster members and are ultimately ejected from the cluster. The majority of escaping black hole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational radiation causes them to coalesce within a few billion years. We predict a black hole merger rate of about 1.6x10-7 yr-1 Mpc-3, implying gravity-wave detection rates substantially greater than the corresponding rates from neutron star mergers. For the first-generation Laser Interferometer Gravitational-Wave Observatory (LIGO-I), we expect about one detection during the first 2 years of operation. For its successor LIGO-II, the rate rises to roughly one detection per day. The uncertainties in these numbers are large. Event rates may drop by about an order of magnitude if the most massive clusters eject their black hole binaries early in their evolution.
预计黑洞双星合并会以引力波的形式释放大量能量。然而，双星演化模型预测的合并率过低，无法引起观测兴趣。在本快报中，我们探讨了黑洞通过与致密恒星系统中的其他恒星发生动力学相互作用而成为紧密双星成员的可能性。在星团中，黑洞在几千万年内成为质量最大的天体；动力学弛豫随后使它们沉入星团核心，在那里它们形成双星。这些黑洞双星通过与其他星团成员的超弹性碰撞而结合得更紧密，并最终从星团中被抛出。大多数逃逸的黑洞双星的轨道周期足够短且偏心率足够高，以至于引力波辐射会导致它们在几十亿年内合并。我们预测黑洞合并率约为1.6×10⁻⁷ 年⁻¹ 百万秒差距⁻³，这意味着引力波探测率将大大高于相应的中子星合并率。对于第一代激光干涉引力波天文台（LIGO - I），我们预计在运行的前两年内大约能探测到一次。对于其继任者LIGO - II，探测率将升至大约每天一次。这些数字的不确定性很大。如果质量最大的星团在其演化早期就将其黑洞双星抛出，事件率可能会下降大约一个数量级。
