Accretion into the central cavity of a circumbinary disc
Accretion into the central cavity of a circumbinary disc
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DOI：
10.1093/mnras/stt1787
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发表时间：
2013-12-01
影响因子：
4.8
通讯作者：
MacFadyen, Andrew
中科院分区：
文献类型：
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作者：
D'Orazio, Daniel J.;Haiman, Zoltan;MacFadyen, Andrew
一个质量接近相等的双星黑洞（BH）可以在环双星吸积盘中清除一个中心空腔;然而，以前的工作已经揭示了进入这个空腔的吸积流。在这里，我们使用二维流体动力学模拟研究吸积流和它们的周期性行为。特别是，我们进行了一系列模拟，涵盖了在0.003 < q < 1范围内的不同二元质量比q = M-2/M-1。在每一种情况下，我们都跟踪了几千个双星轨道，直到它松弛到一个稳定的吸积模式。我们发现了以下结果：（i）双星在维持低密度腔方面是有效的。然而，与具有相同质量的单个BH的盘相比，通过窄相干吸积流进入腔的时间平均质量吸积速率被抑制最多几个因子;（ii）当q大于或接近0.05时，吸积率受到双星的强烈调制，并且依赖于q的精确值，吸积率的功率谱显示出两种情况之一，两个或三个不同的周期;和（iii）为q小于或接近0.05，吸积率变得稳定，没有时间变化。大多数在星系合并中产生的双星的q值都大于或接近0.05。如果这些双星的光度跟踪它们的吸积速率，那么它们的光变曲线的周期图可以帮助它们的识别，并限制它们的质量比和盘属性。
A near-equal-mass binary black hole (BH) can clear a central cavity in a circumbinary accretion disc; however, previous works have revealed accretion streams entering this cavity. Here we use 2D hydrodynamical simulations to study the accretion streams and their periodic behaviour. In particular, we perform a suite of simulations, covering different binary mass ratios q = M-2/M-1 in the range 0.003 < q < 1. In each case, we follow the system for several thousand binary orbits, until it relaxes to a stable accretion pattern. We find the following results: (i) the binary is efficient in maintaining a low-density cavity. However, the time-averaged mass accretion rate into the cavity, through narrow coherent accretion streams, is suppressed by at most a factor of a few compared to a disc with a single BH with the same mass; (ii) for q greater than or similar to 0.05, the accretion rate is strongly modulated by the binary, and depending on the precise value of q, the power spectrum of the accretion rate shows either one, two or three distinct periods; and (iii) for q less than or similar to 0.05, the accretion rate becomes steady, with no time variations. Most binaries produced in galactic mergers are expected to have q greater than or similar to 0.05. If the luminosity of these binaries tracks their accretion rate, then a periodogram of their light curve could help in their identification, and to constrain their mass ratio and disc properties.