Observationally, two main spectral states, i.e., the low/hard state and the high/soft state, are identified in black hole X-ray binaries (BH-XRBs). Meanwhile, the transitions between the two states are often observed. In this paper, we re-investigate the transition luminosities in the framework of the self-similar solution of the advection-dominated accretion flow (ADAF). Specifically, we search for the critical mass accretion rate $\dot m_{\rm crit}$ of ADAF for different radii $r$ respectively. It is found that $\dot m_{\rm crit}$ decreases with decreasing $r$. By testing the effects of BH mass $m$, the magnetic parameter $β$ and the viscosity parameter $α$, it is found that only $α$ has significant effects on $\dot m_{\rm crit}-r$ relation. We define the minimum $\dot m_{\rm crit}$ (roughly at the innermost stable circular orbit) as the hard-to-soft transition rate $\dot m_{\rm tr: H\rightarrow S}$, above which BH will gradually transit from the low/hard state to the high/soft state, and $\dot m_{\rm crit}$ at $30$ Schwarzschild radii as the soft-to-hard transition rate $\dot m_{\rm tr: S\rightarrow H}$, below which BH will gradually transit from the high/soft state to the low/hard state. We derive fitting formulae of $\dot m_{\rm tr: H\rightarrow S}$ and $\dot m_{\rm tr: S\rightarrow H}$ as functions of $α$ respectively. By comparing with observations, it is found that the mean value of $α$ are $α\sim 0.85$ and $α\sim 0.33$ for the hard-to-soft transition and the soft-to-hard transition respectively, which indicates that two classes of $α$ are needed for explaining the hysteresis effect during the state transition. Finally, we argue that such a constrained $α$ may provide valuable clues for further exploring the accretion physics in BH-XRBs.
The X-ray spectral evolution of the ultraluminous X-ray source Holmberg IX X-1
本文对Swift、XMM-Newton和NuSTAR天文台观测到的Holmberg IX X-1原型超亮X射线源（ULX）的X射线谱进行了新的分析。这颗ULX是一个持久的光源，典型的光度约为10^40 erg s^-1，在8年的时间里变化了4 ~ 5倍。我们发现，它的光谱往往演变从相对平坦的或两个组件的光谱中的中等能量带（1-6千电子伏），在较低的光度，光谱是明显弯曲和盘状在最高的光度，与峰值能量在弯曲的光谱往往随着光度的增加而减少。我们认为，ULX的光谱演化可以解释的超级爱丁顿吸积模型，在这种情况下，我们认为ULX的疏散漏斗沿其旋转轴，其大规模的辐射驱动风的范围内。光谱的变化，然后起源于增强的几何光束的吸积率增加，风漏斗变窄，导致从超临界流的中心区域的散射通量比各向同性的热发射风更快地变亮，因此弯曲的硬光谱分量占主导地位，在最高的光度。风也使漏斗边缘的光子向下康普顿散射，导致光谱的峰值能量降低。我们还证实，Holmberg IX X-1显示光谱简并与光度，并建议所观察到的差异自然解释的建议风几何的黑洞旋转轴的进动。
Effects of High-Energy Particles on Accretion Flows onto a Supermassive Black Hole
我们研究了高能粒子对超大质量黑洞吸积流的影响以及逃逸粒子如质子、中子、γ射线和中微子的光度。我们制定了一个一维模型的两个组件的吸积流组成的热粒子和高能粒子，假设释放的能量的一部分被转换为加速的高能粒子。热分量由流体动力学控制，而高能粒子服从扩散-对流方程的矩方程。通过求解这些方程的时间演化，我们得到了平流主导流的稳态解。即使高能粒子的压力超过了热压力，高能粒子对流动结构的影响也很小。对于逃逸质子带走几乎所有释放能量的模型，高能粒子的影响足以使流在内部区域具有开普勒角速度。我们计算这些稳定的解决方案的逃逸粒子的光度。逃逸粒子可以提取从大约$10^{-4}\dot M c^2$到$10^{-2}\dot M c^2$的能量，其中$\dot M$是质量吸积率。逃逸粒子的亮度取决于注入洛伦兹因子、质量吸积率和扩散系数等参数。我们还讨论了逃逸粒子对相对论性喷流产生的影响。
Spirited Away: Advective Loss of Cosmic Rays into the Milky Way's Circumgalactic Medium Explains the Large Magellanic Cloud's Low Gamma-ray Luminosity
Research School of Astronomy & Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）；Centre for the Subatomic Structure of Matter, Adelaide University（阿德莱德大学亚原子结构研究中心）
Accretion geometry in neutron star low-mass X-ray binaries during the hard spectral state
Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
Cyclotron lines in subcritical X-ray pulsars: Monte Carlo simulations reveal the origin of the observed variability
University of Crete（克里特大学）；Institute of Astrophysics, Foundation for Research and Technology-Hellas（希腊研究与技术基金会天体物理研究所）；Princeton University（普林斯顿大学）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）；Ludwig-Maximilians Universität（慕尼黑路德维希-马克西米利安大学）
Two temperature accretion around rotating black holes: Description of general advective flow paradigm in presence of various cooling processes to explain low to high luminous sources
Multi-messenger View of White Dwarf Tidal Disruption Events by Intermediate-Mass Black Holes: I. Gravitational Waves and Disk Photon and Neutrino Emissions
University of Hong Kong（香港大学）；The Hong Kong Institute for Astronomy and Astrophysics, University of Hong Kong（香港大学天体物理研究所）；Shenzhen Institute of Research and Innovation, The University of Hong Kong（香港大学深圳研究院）
