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Origin of the X-Ray Activity in Be/X-Ray Binaries

Be/X 射线双星中 X 射线活动的起源

基本信息

批准号：
13640244
负责人：
OKAZAKI Atsuo
金额：
$ 1.86万
依托单位：
Hokkai-Gakuen University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640244/
关键词：
accretion disks Be stars Be X-ray binaries decretion disks neutron stars resonance tidal interaction X-ray transients 潮汐相互作用ガス円盤

项目摘要

We have studied the interaction between the Be decretion disk and the neutron star in Be/X-ray binaries, by a semi-analytical method and by numerical simulations using a three dimensional Smoothed Particle Hydrodynamics code. We have obtained the following conclusions.1. The Be-star disk in Be/X-ray binaries is truncated at a resonant radius by the negative torque exerted by the neutrons star. The resonant truncation is particularly effective in systems with small or moderate eccentricity and orbital period shorter than several tens of days. In these systems, the material decreted from the Be star accumulates, so that the disk becomes denser more rapidly than if around an isolated Be star.2. The mass-capture rate by the neutron star becomes higher due to weaker resonant truncation in the case of a higher orbital eccentricity and/or a longer orbital period. This explains the trend in the orbital parameters of systems which have shown Type I outbursts (periodic X-ray outbursts).3. An eccentric mode is excited in the Be-star disk through direct driving due to a one-armed bar potential of the binary. The growth time is shorter for a higher orbital eccentricity.4. The mass-capture rate by the neutron star in misaligned systems has a secondary peak, unlike in coplanar systems. For small inclination angles (i【less than or similar】30°) between the Be-star disk and the orbital plane, the secondary peak is much weaker than the primary peak, making a hump in the mass-capture rate profile. However, for large inclination angles (i【greater than or similar】45°), it becomes comparable to the primary peak.5. The material transferred from the Be-star disk forms a time-dependent accretion disk around the neutron star. The disk shrinks at the periastron passage of the Be star and restores its radius afterwards. The accretion rate on to the neutron star is much lower than that of the mass-transfer rate from the Be-star disk.

我们通过半解析方法和使用三维平滑粒子流体动力学代码的数值模拟研究了 Be 衰减盘和 Be/X 射线双星中的中子星之间的相互作用。我们得到以下结论： 1． Be/X 射线双星中的 Be-star 盘在中子星施加的负扭矩的共振半径处被截断。共振截断对于偏心率小或中等且轨道周期短于几十天的系统特别有效。在这些系统中，从 Be 星排出的物质会不断积累，因此与孤立的 Be 星周围相比，盘的密度变得更快。2．在轨道偏心率较高和/或轨道周期较长的情况下，由于共振截断较弱，中子星的质量捕获率变得较高。这解释了显示I型爆发（周期性X射线爆发）的系统的轨道参数的趋势。3．由于双星的单臂杆势，通过直接驱动在 Be-star 盘中激发了一种偏心模式。轨道偏心率越高，生长时间越短。4．与共面系统不同，未对准系统中中子星的质量捕获率有一个次级峰值。对于 Be-star 盘和轨道平面之间的小倾角（即【小于或相似】30°），次峰比主峰弱得多，从而在质量捕获率剖面中形成驼峰。然而，对于大倾角（即【大于或相似】45°），它变得与主峰相当。5。从 Be-star 盘转移的物质在中子星周围形成一个随时间变化的吸积盘。圆盘在 Be 星经过近星体时收缩，随后恢复其半径。中子星的吸积率远低于 Be-star 盘的质量转移率。