Accretion disc dynamics in extreme mass ratio compact binaries
Accretion disc dynamics in extreme mass ratio compact binaries
复制标题
极端质量比致密双星中的吸积盘动力学
DOI：
10.1111/j.1365-2966.2007.11437.x
复制
发表时间：
2007
影响因子：
4.8
通讯作者：
M. Truss
中科院分区：
文献类型：
--
作者：
M. Truss
对质量比为Q=M2/M1<；0.1的双星系统中吸积盘的动力学和几何性质进行了数值研究，适用于超致密X射线双星、AM CVN星和甚短周期激变变星。在二元参考系中，圆盘的稳态几何形状与较高质量比时的预期几何形状有很大的不同。对于Q∼0.1时，圆盘呈现出通常的椭圆形状，其长轴垂直于两颗恒星的中心线。然而，在较小的质量比时，圆盘外部区域的椭圆形气体轨道在双星平面内旋转。旋转角随着气体温度的升高而增大，但与Q成反比。在Q=0.01时，这些轨道的长轴几乎平行于两颗恒星的中心线。这些效应可能是从Q=0.02的AM CVN星GP Com的多普勒层析中推断出类似的盘结构的原因。低质量比时的稳态几何形状不能用气体轨道的无粘性、限制性三体模型来预测；它与罗氏叶边界附近圆盘的潮汐-粘性截断效应有关。由于某些系统的盘面几何形状可以通过观测推断出来，因此这可能为确定超致密双星的质量比提供有用的诊断。
An analysis is presented of a numerical investigation of the dynamics and geometry of accretion discs in binary systems with mass ratios q = M 2 /M 1 < 0.1, applicable to ultracompact X-ray binaries, AM CVn stars and very short period cataclysmic variables. The steady-state geometry of the disc in the binary reference frame is found to be quite different from that expected at higher mass ratios. For q ∼ 0.1, the disc takes on the usual elliptical shape, with the major axis aligned perpendicular to the line of centres of the two stars. However, at smaller mass ratios the elliptical gaseous orbits in the outer regions of the disc are rotated in the binary plane. The angle of rotation increases with gas temperature, but is found to vary inversely with q. At q = 0.01, the major axis of these orbits is aligned almost parallel to the line of centres of the two stars. These effects may be responsible for the similar disc structure inferred from Doppler tomography of the AM CVn star GP Com, which has q = 0.02. The steady-state geometry at low mass ratios is not predicted by an inviscid, restricted three-body model of gaseous orbits; it is related to the effects of tidal-viscous truncation of the disc near the Roche lobe boundary. Since the disc geometry can be inferred observationally for some systems, it is proposed that this may offer a useful diagnostic for the determination of mass ratios in ultracompact binaries.