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

• 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

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三维平滑粒子流体动力学程序的数值模拟研究了Be/X射线双星中Be衰变盘和中子星之间的相互作用，得到了以下结论。 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，共振截断在具有中子星的系统中特别有效。小或中等的偏心率和短于几十天的轨道周期在这些系统中，从Be星中排出的物质会不断积累，从而使盘变得比在孤立的Be星周围更快地致密。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，中子星的中子星的轨道参数变得较高，这解释了显示I型爆发的系统的轨道参数的趋势。 （周期性X射线爆发）.3.由于双星的单臂杆势，Be-star盘中会激发偏心模式。轨道偏心率越高，生长时间越短。与共面系统不同，在未对准的系统中，中子星的质量捕获率有一个次级峰值，对于 Be-星盘和轨道平面之间的小倾角（小于或相似），次要峰比主要峰弱得多，从而在质量捕获速率曲线中形成驼峰。但是，对于大倾角（大于或相似）45°，它变得与主要峰材料相当。5。从Be星盘转移出来的物质在中子星周围形成了一个随时间变化的吸积盘，该吸积盘在Be星经过近星体时收缩，之后又恢复到中子星上的吸积速率。低于 Be-star 盘的传质速率。