X射线双星谱态跃迁的光学/紫外辐射特征和物理机制

X-ray binaries are multiwavelength objects with detectable emission from radio to X-rays or even gamma-rays and at all wavelengths in between. The emission in different band can inform us of the different components emitting. So the multiwavelength monitoring observations of X-ray binaries can play a key role in fully understanding the accretion and ejection processes. The traditional definition of spectral state mainly based on the X-ray spectral and timing properties, which can not trace the interaction between accretion flow and jet. But we know the coupling between accretion and jet is different across different spectral states. This project will seek an improved understanding of this issue through the analysis of archival and new Swift data including optical, ultraviolet, soft X-ray and hard X-ray for both black hole and neutron star X-ray binaries. We also will develop fast optical photometric observation based on our advanced fast read-out CCD and trigger target of opportunity observation during sate transition. The aim of this project is to study the optical and ultraviolet emission across state transition in different individual X-ray binary. These results will constrain the origin of optical and ultraviolet emission across different spectral states. We hope to find more evidence that the optically thick emission can extend to optical/ultraviolet band, and further estimate the break frequency of jet emission. Then we want to discuss some important issues based on the theory of accretion flow and jet, including the total power of jet, some properties of jet, the triggering mechanism of jet quenching, the interaction between the jet and the accretion flow during state transition..

X射线双星的辐射覆盖从射电到X射线甚至到伽马射线, 而且不同波段的辐射可能来自不同的物理成分, 因此研究X射线双星的多波段辐射是全面研究X射线双星的吸积和喷流过程的重要手段。之前关于X射线双星的谱态的定义主要基于X射线的能谱和光变特征，因此需要从多波段的角度研究谱态以及谱态跃迁。本项目主要利用已有的空间X射线卫星Swift的多波段（包括光学、紫外、软X射线和硬X射线）档案数据，研究谱态跃迁过程的光学/紫外辐射的特征，以及和X射线辐射之间的关系，并且结合地面望远镜的光学快速测光观测以及针对谱态跃迁的多波段机遇对象观测所得到的第一手观测数据，限制谱态跃迁期间光学/紫外辐射的起源，从而为喷流辐射的光学厚成分可以延伸光学/紫外波段寻找更多的证据，进而估算喷流辐射的截断，结合相关的吸积和喷流的理论模型，探讨喷流的总功率，触发喷流熄灭的机制，喷流的熄灭和谱态跃迁的关系等物理问题。

X射线双星暂现源的爆发是研究吸积物理的重要观测对象，很多的爆发过程伴随着X射线能谱态的演化，这些不同的能谱态被认为和吸积率，吸积几何以及喷流行为息息相关。本项目系统地研究了RXTE时代小质量X射线双星的明亮爆发，获得了爆发特征的统计结果。并以此研究为基础，拓展到研究中等质量候选体ESO 243-49 HLX-1的爆发演化和能谱态跃迁，通过和X射线双星爆发进行对比进而限制爆发机制和中心天体的属性。我们又在黑洞暂现源GRS 1739-278中的迷你爆发中第一次发现了能谱态跃迁过程，并且发现态跃迁光度和明亮爆发符合相同的关系，表明不同类型的爆发中的态跃迁光度由同样的物理机制决定。此外我们从文献中收集了低光度活动星系核NGC 7213的长达40年的X射线观测数据，发现其光变曲线符合快速上升指数下降的形态，该光变曲线可以成功的用超大质量黑洞的潮汐撕裂事例来解释，从而使得这次长时标的闪耀成为了一次特殊的潮汐撕裂事例候选体。此外项目负责人及其合作者多次获得针对X射线双星爆发的机遇对象观测，覆盖波段从射电、光学、紫外和X射线，从而获得了丰富的爆发期间的多波段数据。