Gas Accretion from a Circumbinary Disk
Gas Accretion from a Circumbinary Disk
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来自环形盘的气体吸积
DOI：
10.1088/0004-637x/708/1/485
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
K. Ando
中科院分区：
文献类型：
--
作者：
T. Hanawa;Y. Ochi;K. Ando
提出了一种新的计算方法来研究环双星盘的气体吸积。该方案将气体速度分解为两个分量，其中一个表示开普勒旋转，另一个表示偏离开普勒旋转。这种方案使我们能够以更好的精度解决气体盘对重力的离心平衡，因为以前的惯性力抵消了重力。它适用于围绕双星旋转的、主次质量比为1.4:0.95的环双星盘。重力只在主星和次星周围的小圆形区域被人为地减弱。其半径为二值分离的7%，比以往基于网格的模拟要小得多。建立了七个模型来研究气体温度和盘的初始内半径的依赖关系。当假设双星有一个圆形轨道时，气体的吸积表现出快速和缓慢的时间变化。时间的变化是由于环双星盘中螺旋臂的振荡。主盘和副盘的质量在振荡过程中明显增加。主盘的质量吸积率往往更高，但在某些时期，从盘的质量吸积率更高。在后期的波动中，即在双星旋转超过20次之后，两个分量的吸积速率是相似的。由于气流的冲击，主圆盘受到强烈的扰动，因此外层被移除了。相反，从盘在大多数时间是安静的。主盘和副盘都有行螺旋波，在它们内部传递角动量。
A new computational scheme is developed to study gas accretion from a circumbinary disk. The scheme decomposes the gas velocity into two components one of which denotes the Keplerian rotation and the other of which does the deviation from it. This scheme enables us to solve the centrifugal balance of a gas disk against gravity with better accuracy, since the former inertia force cancels the gravity. It is applied to circumbinary disk rotating around binary of which primary and secondary has mass ratio, 1.4: 0.95. The gravity is reduced artificially softened only in small circular regions around the primary and secondary. The radii are 7% of the binary separation and much smaller than those in the previous grid based simulations. Seven models are constructed to study dependence on the gas temperature and the initial inner radius of the disk. The gas accretion shows both fast and slow time variations while the binary is assumed to have a circular orbit. The time variation is due to oscillation of spiral arms in the circumbinary disk. The masses of primary and secondary disks increase while oscillating appreciably. The mass accretion rate tends to be higher for the primary disk although the secondary disk has a higher accretion rate in certain periods. The accretion rates onto the two components are similar within the fluctuations in late times, ie, after the binary rotates more than 20 times. The primary disk is perturbed intensely by the impact of gas flow so that the outer part is removed. The secondary disk is quiet in most of time on the contrary. Both the primary and secondary disks have traveling spiral waves which transfer angular momentum within them.