磁化中子星的变不透明度与吸积柱状态
Variable opacity and accretion-column regimes of magnetized neutron stars
- Friedrich-Alexander Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡大学）
- Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）
- Tel Aviv University（特拉维夫大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文研究磁化中子星吸积柱的不同状态，提出确定临界吸积率的方法，并发现有效冷却与对流解共存区域，其振荡可能与观测到的准周期振荡相关。
AI中文摘要：
辐射支持的磁化中子星吸积柱可以在几种不同的状态下运行。随着吸积率的增加，磁层吸积可能通过热点发射、有效冷却的辐射激波以及对流下沉柱进行。吸积流的结构由全局参数（如磁场强度和物质吸积率）决定，但也受到强磁场中不透明度变化的影响。对于能量低于回旋能量的光子，其不透明度的降低能够显著提高经典临界吸积率，该临界吸积率将有效冷却解与对流解分开。我们提出了一种方法来确定临界吸积率，超过该吸积率时，Basko-Sunyaev下沉解变得不可避免。我们还使用Basko-Sunyaev下沉解来估算等离子体温度，并将特征光子能量与局部回旋能量进行比较。对于中等磁场和高吸积率的组合，对流柱中的特征光子能量通常超过回旋能量。在这种情况下，不透明度不会因磁场而降低，从而形成高耸的吸积柱。强磁场系统可能在广泛的超爱丁顿吸积率范围内保持短而有效冷却的吸积柱。我们确定了吸积率和磁场强度中的一个区域，在该区域中，有效冷却解和对流解可能共存。在这个区域中，吸积柱可能在状态和几何形状之间切换或振荡。这种振荡的典型时间接近吸积柱的补充时间，或接近其底部的热时间。在一些超爱丁顿天体上观测到的1-100 mHz频率范围内的准周期振荡可能与这种弛豫循环有关。
英文摘要：
Radiation-supported accretion columns of magnetized neutron stars can operate in several distinct regimes. As the accretion rate increases, magnetospheric accretion may proceed through hot-spot emission, efficiently cooling radiative shocks, and advective sinking columns. The structure of the accretion flow is determined by the global parameters such as magnetic field strength and mass accretion rate, but is also affected by opacity variations in strong magnetic fields. A decrease of opacity for photons with energy below the cyclotron energy is able to substantially augment the classical critical accretion rate separating efficiently cooling solutions from advective solutions. We propose an approach to determine the critical accretion rate above which the Basko-Sunyaev sinking solution becomes unavoidable. We also use the Basko-Sunyaev sinking solution to estimate the plasma temperature and compare the characteristic photon energy with the local cyclotron energy. For a combination of moderate magnetic fields and high accretion rates, the characteristic photon energy in advective columns typically exceeds the cyclotron energy. In this case, the opacity is not reduced by the magnetic field, and tall accretion columns are formed. Strong magnetic-field systems may retain short, efficiently cooling accretion columns over a wide range of super-Eddington accretion rates. We identify a region in accretion rate and magnetic-field strength where both efficiently cooling and advective solutions may coexist. In this region, the column may switch or oscillate between the regimes and geometries. The typical time of such oscillations are close to the replenishment time of the column, or to the thermal time near its bottom. The quasi-periodic oscillations, observed in some super-Eddington objects in the 1-100 mHz frequency range, may be related to such relaxation cycles.
