黑洞X射线双星态跃迁相关观测现象的理论研究

The timing and spectral information of black hole X-ray binaries are of crucial importance to our understanding on accretion processes in compact systems. Jets are observed to be associated with the accretion flows. The jet emerges during the state transition (from hard state to soft state) of X-ray binaries is significantly different from that in the hard state. The former is episodic, while the latter is continuous. Although numerous observations have been carried out and large amounts of data are collected, the formation mechanism of episodic jet (ejection) still remains unclear, the only theory, to our knowledge, with solid dynamical base is an MHD model recently proposed by Yuan et al.. Based on this MHD episodic ejection model, we will, through this project, present convincing physical explanations on several major properties of X-ray binaries observed in their state transitions (e.g., dip-flare pattern, huge amount of energy ejected, the gap between two ejections, the time-lag on different wavelengths, and high polarization). Besides, we will also benefit from this project on the understanding of the relationship/link between hot accretion flow and (episodic) jets.

黑洞X射线双星有着丰富的光变及谱态变化信息，对我们了解黑洞的吸积过程有极其重要的意义。黑洞双星的吸积往往伴随着喷流的存在。但是硬态时的喷流和硬软态跃迁时的喷流有显著的不同，分别为连续性喷流和间歇性喷流。目前对态跃迁阶段的间歇性喷发过程已经积累了大量丰富的观测数据，但对间歇性喷流的形成机制仍然不明确，袁等人提出的间歇性喷流的磁流体动力学形成机制是目前唯一具有动力学基础的理论模型。基于此间歇性喷流理论模型，本项目将研究黑洞双星态跃迁时的几个主要的观测现象（如硬X射线下降-射电爆发现象，巨大的爆发能量，多个爆发间的间隔，不同波段的时延，以及高偏振度等等），力图给出相应的物理解释。此外，本课题的顺利开展，也将加深我们在热吸积流-（间歇性）喷流相互关系上的认识。

黑洞热吸积流模型是黑洞双星硬态以及低光度活动星系核的主流理论模型。在本基金的支持下，我们系统全面地研究了黑洞热吸积流的动力学和辐射过程，取得了一系列的成果。.重点来说，我们给出了黑洞热吸积流的辐射效率函数，该函数有广泛的应用；在广义相对论框架下，我们详细研究了黑洞热吸积流中的质子通过pp碰撞所带来的伽马辐射，并通过观测数据来验证、限制理论模型；我们研究了射电-X射线相关关系、X射线光谱谱型跟X射线光度相关关系等，观测上这些相关关系有望用来更好地确定系统的吸积机制；我们发现不同系统中的喷流有高度的相似性，对喷流理论提供了严重的限制；我们首次尝试进入观测领域，申请并获得了美国VLBA 16小时的观测，用来研究极低光度活动星系核的射电起源问题。