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Numerical Simulations of Accretion Flows onto a Compact Object in a Close Binary System

封闭二元系统中紧凑物体吸积流的数值模拟

基本信息

批准号：
61540183
负责人：
MATSUDA Takuya
金额：
$ 1.34万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61540183/
关键词：
Accretion X-Ray Stars Spinup Spindown Galaxy Spiral Arm Numerical Simulation アクリーション円盤 X線パルサー近接連星系

项目摘要

Numerical simulations on an accretion flow and a related problem were performed. There are two types of accretion flow in a close binary system depending on the mangitude of the angular momentum of the accreting gas: a Roche lobe overflow and a wind-fed accretion. In the former case we have pointed out the existence of spiral shock waves on an accretion disc. In the present work our numerical results show good agreement with the anlytic solution obtained by Spruit. According to his theory there is a close relation between the pitch angle of the spiral shocks and the specific heat ratio. The smaller the specific heat ratio, the smaller the pitch angle. We have shown that accretion can occur even without a viscosity in some cases.Relating to the problem of the accretion, we have investigated the problem of spiral arm formation in a disc galaxy. In our view, the cause of spiral arms are a deviatin of gravitational force from the exact axisymmetry. In the accretin disc very similar phenomenon occurs due to the tidal force.We have also investigated the wind-fed accretion and the angular momentum accretion on to a compact object in a close binary system. We found that the flow is unsteady and the sign of the angular momentum of the accreting gas changes randomly with time. Although this is an unexpected result, Taam & Fryxcell in USA recently confirmed our results by their extensive numerical simulations. We have very new picture on the spin-up/down phenomena of a compact object. Our results can explain observations well.

对吸积流及相关问题进行了数值模拟。在密近双星系统中，根据吸积气体角动量的大小，存在两种吸积流：洛希瓣溢出和风吸积。在前一种情况下，我们指出了吸积盘上螺旋激波的存在。在目前的工作中，我们的数值计算结果表明，与Spruit得到的分析解很好的协议。根据他的理论，螺旋激波的螺距角与比热比之间有密切的关系。比热比越小，螺旋角越小。我们证明了在某些情况下即使没有粘性也会发生吸积。与吸积问题有关，我们研究了盘星系中旋臂的形成问题。在我们看来，螺旋臂的形成是由于重力偏离了精确的轴对称。在吸积盘中，由于潮汐力的作用，也发生了类似的现象。我们还研究了密近双星系统中致密天体的风吸积和角动量吸积。我们发现，流动是不稳定的，吸积气体的角动量的符号随时间随机变化。虽然这是一个意想不到的结果，美国的Taam和Fryxcell最近通过他们广泛的数值模拟证实了我们的结果。我们对致密物体的上旋/下旋现象有了新的认识。我们的结果可以很好地解释观测结果。