Evolution of warped and twisted accretion discs in close binary systems
Evolution of warped and twisted accretion discs in close binary systems
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DOI：
10.1051/0004-6361/200913088
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发表时间：
2009-12
影响因子：
6.5
通讯作者：
M. Fragner;R. Nelson
中科院分区：
文献类型：
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作者：
M. Fragner;R. Nelson
上下文在双星系统中有许多吸积盘的例子，其中吸积盘的中平面被认为是相对于双星轨道平面倾斜的。目标。我们的目的是研究在错位双星系统中出现的详细盘结构，它是盘的纵横比、粘度参数α、盘的外半径R和双星倾角γF的函数。我们的目的也是研究条件，导致一个倾斜的光盘被破坏的强烈的差异进动。方法.我们使用基于网格的流体动力学代码来执行3D模拟。与以往研究斜盘所用的SPH格式相比，本程序具有较低的数值粘性。这使得粘度对disc演变的影响得到严格控制。结果我们发现，对于α较低的厚圆盘（h = 0.05），圆盘中有效的翘曲通讯使它们能够作为刚性体旋进，几乎没有翘曲或扭曲。观察到这种盘在粘性演化时间上与双星轨道平面对齐。具有较高粘度的较薄的圆盘，其中经纱通信效率较低，在实现刚体旋进状态之前产生显著的扭转。在我们考虑的最极端的条件下（h = 0.01，α = 5× 10−3和α = 0.1），我们发现圆盘可以被强的差旋进破坏。变得高度扭曲的圆盘可能在比粘性时标短得多的时标上（可能在进动时间上）与双星轨道平面对齐。结论.我们发现协议与以前的研究表明，较厚的低粘度的dscs的经验温和的翘曲和严格的过程。我们还发现，灰分大幅减少，光盘可能会被破坏的强微分进动，但光盘的厚度是显着小于（h = 0.01）比以前的研究中发现的（h = 0.03）。
Context. There are numerous examples of accretion discs in binary sys tems where the disc midplane is believed to be inclined relat iv to the binary orbit plane. Aims. We aim to examine the detailed disc structure that arises in a mis ligned binary system as a function of the disc aspect rat io h, viscosity parameterα, disc outer radiusR, and binary inclination angleγF . We also aim to examine the conditions that lead to an incline d disc being disrupted by strong di fferential precession. Methods. We use a grid-based hydrodynamic code to perform 3D simulati ons. This code has a relatively low numerical viscosity comp ared with the SPH schemes that have been used previously to study i nclined discs. This allows the influence of viscosity on the d isc evolution to be tightly controlled. Results. We find that for thick discs ( h = 0.05) with lowα, efficient warp communication in the discs allows them to precess as rigid bodies with very little warping or twisting. Such discs are observe d to align with the binary orbit plane on the viscous evolutio n time. Thinner discs with higher viscosity, in which warp communication is less e fficient, develop significant twists before achieving a state o f rigid-body precession. Under the most extreme conditions we consider ( h = 0.01,α = 5× 10−3 andα = 0.1), we find that discs can become broken or disrupted by strong di fferential precession. Discs that become highly twisted are o bs rved to align with the binary orbit plane on timescales mu ch shorter than the viscous timescale, possibly on the precession time . Conclusions. We find agreement with previous studies that show that thick d scs with low viscosity experience mild warping and precess rigidly. We also find that ash is decreased substantially, discs may be disrupted by stron g differential precession, but for disc thicknesses that are significantly less ( h = 0.01) than those found in previous studies ( h = 0.03).