The Gravitational waves merger time distribution of binary neutron star systems
The Gravitational waves merger time distribution of binary neutron star systems
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DOI：
10.1093/mnras/stz1589
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发表时间：
2019-03
影响因子：
4.8
通讯作者：
P. Beniamini;T. Piran
中科院分区：
文献类型：
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作者：
P. Beniamini;T. Piran
双星合并是r过程核合成的主要场所.它们的速率决定了银河系中重元素的化学演化。BNS的合并率是它们的出生率与引力辐射旋入延迟时间的卷积。使用所观察到的银河系BNS人口，我们在这里表明，在所观察到的BNS中的恒星的寿命是足够短的BNS的年龄有很少或没有影响所观察到的合并时间分布。我们发现，在后期（$t\gtrsim 1$ Gyr）的引力波延迟时间分布（DTD）遵循预期的$ t^{-1}$。然而，在较短的时间内，迅速合并的系统（在整个人口的40 -60美元之间）明显过剩。虽然DTD的确切形状不能用现有的数据来确定，但在充分描述数据的所有模型中，我们发现至少有40美元的合并时间小于1Gyr的BNS。这种人口的快速合并意味着下降的沉积速率的$r$-过程的材料，这是符合几个独立的观测重元素丰度在银河系。与此同时，这种要求双星初始间隔大约为一个太阳半径的人口清楚地表明，这些双星有共同的包络祖先。我们的研究结果表明，未来的LIGO/Virgo BNS合并的一个重要部分将驻留在星星形成星系。
Binary neutron stars (BNS) mergers are prime sites for $r$-process nucleosynthesis. Their rate determines the chemical evolution of heavy elements in the Milky Way. The merger rate of BNS is a convolution of their birth rate and the gravitational radiation spiral-in delay time. Using the observed population of Galactic BNS we show here that the lifetimes of pulsars in observed BNSs are sufficiently short that the ages of BNSs have little to no effect on the observed merger time distribution. We find that at late times ($t\gtrsim 1$ Gyr) the gravitational wave delay time distribution (DTD) follows the expected $ t^{-1}$. However, a significant excess of rapidly merging systems (between $40-60\%$ of the entire population) is apparent at shorter times. Although the exact shape of the DTD cannot be determined with the existing data, in all models that adequately describe the data we find at least $40\%$ of BNSs with merger times less than 1Gyr. This population of rapid mergers implies a declining deposition rate of $r$-process materials that is consistent with several independent observations of heavy element abundances in the Milky Way. At the same time this population that requires initial binary separations of roughly one solar radius clearly indicates that these binaries had common envelope progenitors. Our results suggest that a significant fraction of future LIGO/Virgo BNS mergers would reside in star forming galaxies.