Long-term evolution of accretion discs in Be/X-ray binaries
Long-term evolution of accretion discs in Be/X-ray binaries
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DOI：
10.1111/j.1365-2966.2006.10917.x
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发表时间：
2006-08
影响因子：
4.8
通讯作者：
K. Hayasaki;K. Hayasaki;A. Okazaki
中科院分区：
文献类型：
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作者：
K. Hayasaki;K. Hayasaki;A. Okazaki
本文用数值方法研究了短周期中等偏心率共面Be/X射线双星中中子星星周围吸积盘的长期演化。从三维光滑粒子流体动力学模拟，我们发现，光盘通过三个不同的阶段，每个阶段的特点是不同的质量吸积模式的演变。在第一个“发展阶段”，圆盘形成并向近似开普勒圆盘发展。它有一个相对较大的双峰质量吸积率，其中较高的峰值由近星点的直接吸积引起，其次是较低的峰值，由单臂螺旋波引起的吸积。在第二个“过渡阶段”，圆盘近似开普勒，并随时间增长。质量吸积率随着圆盘的增大而增大。在第二阶段，有一个过渡的质量吸积率从双峰到单峰模式。在最后的准稳态，质量吸积率是平均平衡的质量转移率从被盘，并表现出定期的轨道调制。在准稳态下，质量吸积率有一个单峰，这是由波致吸积在过渡阶段的后期阶段所造成的。X射线最大值的轨道调制不仅可以提供盘宿存的间接证据，而且还可以提供盘演化状态的观察诊断。
We numerically study the long-term evolution of the accretion disc around the neutron star in a coplanar Be/X-ray binary with a short period and a moderate eccentricity. From three-dimensional smoothed particle hydrodynamics simulations, we find that the disc evolves through three distinct phases, each characterized by different mass-accretion patterns. In the first ‘developing phase’, the disc is formed and develops towards a nearly Keplerian disc. It has a relatively large, double-peaked mass accretion rate with the higher peak caused by the direct accretion at periastron, which is followed by the lower peak that is caused by the accretion induced by a one-armed spiral wave. In the second ‘transition phase’, the disc is approximately Keplerian and grows with time. The mass-accretion rate increases as the disc grows. In the second phase, there is a transition in the mass-accretion rate from a double-peaked to a single-peaked pattern. In the final quasi-steady state, the mass-accretion rate is on average balanced with the mass-transfer rate from the Be disc and exhibits a regular orbital modulation. In the quasi-steady state, the mass accretion rate has a single peak that is caused by the wave-induced accretion as in a later stage of the transition phase. The orbital modulation of X-ray maxima could provide not only circumstantial evidence for the persistent disc but also an observational diagnosis of the disc evolutionary state.