银河系激变变星的统计研究

Cataclysmic variables (CVs) are important X-ray sources in the Milky Way galaxy. Previous works have greatly improved our understanding of CVs yet still leave some important questions to be answered. Firstly, a self-consistent model including both the intrinsic absorption and emission needs to be constructed to describe the hard X-ray emission from magnetic and non-magnetic CVs; Secondly, a quantitative study on sub classes of CVs are required to better understand their statistical properties; Thirdly, a thorough population synthesis work is needed to be compared to each and every aspect of observational results..We are planning to make use of X-ray data of Suzaku, Nustar, Chandra (and HMXT if possible) to investigate X-ray emission of CV population. We will start with nearby CVs. By building the respective absorption and emission models, we will try to find a more reliable shock temperature - White Dwarf mass (or the T-M) correlation. Next, we are going to study the Galactic Bulge/Ridge/Center X-ray Emission, which represent complete samples of CVs and active binary stars. This sample could enable the statistical investigation of CVs, such as the relative numbers of magnetic and non-magnetic CVs, the white dwarf mass distribution and the luminosity functions. Last but not least, we are planning to simulate the statistical properties of CVs by incorporating binary evolution and population synthesis methods. These results would then be compared to observational ones to put constraints to key processes and key parameters in CV evolution, and improve our understanding on binary stars containing white dwarf stars.

激变变星是星系内重要的X射线源。目前其观测和理论研究还存在一些重要的问题有待解决。首先，需要一个物理上自洽的内禀吸收和X射线辐射模型；第二，缺少对其子类的统计性质的定量研究;第三，需要一个与各种观测结果进行定量比较的星族合成工作。我们计划利用Suzaku、Nustar、Chandra X射线卫星（如有可能还将利用我国的HMXT卫星）对近邻激变变星和银河系核球、银心的观测数据，首先建立相应的内禀吸收和辐射模型;然后探寻银河系核球中各子类激变变星的统计性质，如磁和非磁激变变星的比例、白矮星质量分布、光度函数等;最后利用双星演化和星族合成的方法模拟激变变星演化和星族的整体性质，限制激变变星演化中的重要物理过程和物理参数，并进一步推进对含白矮星的双星的整体认识。

处于银河系不同位置的激变变星的统计性质与其形成和演化过程密切相关，因此也反映了其所处环境的影响。为了对上述问题进行系统的研究，我们发展了利用X射线谱线测量激变变星中白矮星质量的方法，对太阳系近邻、核球以及银核中的激变变星的统计性质进行了研究。还利用X射线、紫外和光学数据以及恒星演化模型，研究了V1082 Sgr和强紫外AGB星Y Gem的物理本质。项目还利用Gaia和XMM-Newton数据，对150pc以内的激变变星进行了系统的分析。.对太阳系近邻、核球和银核的激变变星的研究显示，核球和太阳系近邻的激变变星的性质相似，而银核中的激变变星则可能含有大质量（~1.2个太阳质量）的白矮星。这预示着其中的双星演化历史与核球截然不同，可能是在银核的高恒星密度环境中，受到动力学演化的影响较大导致的。对V1082 Sgr 和Y Gem的研究显示，V1082 Sgr很有可能是高磁场激变变星，而Y Gem则很可能是白矮星和AGB星组成的共生星系统，白矮星通过吸积AGB星星风，辐射出明亮的X射线和紫外辐射。更重要的是，后者预示着，我们可以通过系统的搜寻有紫外盈余的AGB星，来寻找低吸积率，低光度的共生星。这对理解共生星的形成、演化和星族都有着重要意义。项目以150pc内激变变星的性质为依据，给出了500pc内激变变星的候选体 。下一步工作可以以此展开，研究暗弱激变变星的星族性质。