SUPERORBITAL PHASE-RESOLVED ANALYSIS OF SMC X-1
SUPERORBITAL PHASE-RESOLVED ANALYSIS OF SMC X-1
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SMC X-1 的超轨道相位分辨分析
DOI：
10.1088/0004-637x/773/1/58
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Yi
中科院分区：
文献类型：
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作者：
Chin;Y. Chou;Ting;Yi
高质量X射线双星SMC X-1是一颗食双星，轨道周期为3.89天。该系统表现出超轨道调制，周期在240天至265天之间变化。超轨道调制的瞬时频率和相应的相位可以通过最近发展的时频分析技术，希尔伯特-黄变换（HHT）获得。我们提出了一个相位分辨分析的光谱和轨道轮廓与超轨道相位来自HHT。由Rossi X射线定时探测器上的比例计数器阵列观测到的X射线光谱与黑体加康普顿化分量很好地拟合。等离子体光学深度是物质沿视线沿着分布的良好指标，与在2.5-25 keV下检测到的通量显著反相关。然而，等离子体光学深度与等效铁谱线宽度之间的关系并不是单调的。当辐射强度大于35 mCrab时，相关性不显著，但当辐射强度小于20 mCrab时，相关性明显。这表明在不同的超轨道相中，该双星系统的不同区域控制着铁线的产生。为了研究轨道轮廓对超轨道相位的依赖性，我们对不同的超轨道状态，通过将全天监视器光变曲线与轨道周期折叠，得到了日食轮廓。在超轨道过渡态期间，发现了一个与Her X-1的食前倾角相似的倾角特征，位于轨道相位θ 0.6-0.85。这表明吸积盘有一个凸起，吸收相当多的X射线辐射的流盘相互作用区域。倾角宽度与流量呈反相关关系，这种关系可以用旋进倾斜吸积盘的情形来解释。
The high-mass X-ray binary SMC X-1 is an eclipsing binary with an orbital period of 3.89 days. This system exhibits a superorbital modulation with a period varying between ∼40 days and ∼65 days. The instantaneous frequency and the corresponding phase of the superorbital modulation can be obtained by a recently developed time–frequency analysis technique, the Hilbert–Huang transform (HHT). We present a phase-resolved analysis of both the spectra and the orbital profiles with the superorbital phase derived from the HHT. The X-ray spectra observed by the Proportional Counter Array on board the Rossi X-ray Timing Explorer are fitted well by a blackbody plus a Comptonized component. The plasma optical depth, which is a good indicator of the distribution of material along the line of sight, is significantly anti-correlated with the flux detected at 2.5–25 keV. However, the relationship between the plasma optical depth and the equivalent width of the iron line is not monotonic. There is no significant correlation for fluxes higher than ∼35 mCrab but clear positive correlation when the intensity is lower than ∼20 mCrab. This indicates that the iron line production is dominated by different regions of this binary system in different superorbital phases. To study the dependence of the orbital profile on the superorbital phase, we obtained the eclipse profiles by folding the All Sky Monitor light curve with the orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip in Her X-1, lying at orbital phase ∼0.6–0.85, was discovered during the superorbital transition state. This indicates that the accretion disk has a bulge that absorbs considerable X-ray emission in the stream–disk interaction region. The dip width is anti-correlated with the flux, and this relation can be interpreted by the precessing tilted accretion disk scenario.