利用HXMT研究X射线双星能谱特征与光度的演化关系

X-ray binaries are the core science program of the HXMT observations. The high energy emissions in X-ray binaries reflect the activity near compact objects, probing the physics in the ultra-strong gravity, strong magnetic field and ultra-high density. HXMT can measure the broad X-ray spectra from 1- 250 keV in X-ray binaries including black holes and neutron stars, then can obtain both the thermal and non-thermal spectra, which will help to search for the iron absorption line and cyclotron absorption features. In this program, we will analyze the spectra of X-ray binaries to study the relations between the inner radius of the accretion disk and X-ray luminosity, and search for the iron absorption line features and study variations of iron absorption line with luminosities, so that we can find the evidence of outflows in X-ray binaries. In addition, we will study the variation of the cyclotron absorption line features with luminosities in neutron star X-ray binaries, which will probe the strong magnetic field and geometry of accretion column, radiation mechanism near the surface of neutron stars.

X射线双星是慧眼卫星HXMT的核心科学目标之一。X射线双星高能辐射反映了致密天体剧烈活动的物理特征，是探测宇宙强引力场、致密物质、超强磁场环境的探针。HXMT可以精确测量X射线双星（黑洞和中子星系统）宽波段X射线能谱（1-250 keV）,同时获得热辐射和非热辐射的能谱，并有助于搜寻铁吸收线和回旋吸收线的谱线特征。本项目将通过能谱精细分析来研究黑洞和中子星X射线双星的吸积盘内半径与光度的关系，搜寻铁吸收线并研究其与光度的关系，来寻找X射线双星中物质外流的证据。研究中子星双星的回旋吸收线特征参数与光度的关系，研究中子星表面磁场及吸积柱的物理特征和辐射机制。

本项目主要利用慧眼科学卫星对X射线双星系统开展X射线的细致分析，取得了四个方面的主要研究成果。第一，黑洞X射线双星辐射性质特别是吸积和外流的演化特征，发现黑洞X 射线双星中向外高速运动的冕，对理解黑洞吸积和动力学演化有重要意义。第二，发现中子星最高能量回旋吸收线，并研究谱线能量特殊变化规律，对理解中子星吸积柱几何变化有重要指导价值。第三，首次利用小波分析方法研究中子星双星系统，发现中子星光变中存在低频暂现准周期振荡现象，对理解中子星吸积过程及光变特征给出新的线索。第四，多波段研究X射线双星系统并研究其本质，特别发现一些新的激变变星，对研究磁白矮星的物理性质有重要价值。我们的研究成果获得了国内外同行的关注，并有其他的科学收获，对推动和拓展慧眼卫星科学目标也起到了重要意义。