论文标题
使用Hilbert-Huang Transform在4U 1636-53中对MHz准周期振荡的相分辨分析
Phase-resolved analyses of mHz quasi-periodic oscillations in 4U 1636-53 using Hilbert-Huang transform
论文作者
论文摘要
我们在4U 1636-536中，基于Millihertz Quasi periodic振荡（MHz QPOS）的Hilbert-Huang Transform（HHT）的相分辨光谱。在I型X射线突发之前，可以检测到大约几千秒钟的〜8 MHz QPO。它被解释为在中子星表面上略有稳定的燃烧。在这项研究中，我们使用HHT分析了2007年至2009年之间XMM-Newton收集的数据。HHT是一种强大的工具，使我们能够获得QPOS等非平稳周期性现象的瞬时频率，幅度和相位。有了明确的相位，可以精确地揭示出4U 1636-53的〜8 MHz QPO的振荡曲线。除了振荡曲线外，还构建了完整循环的相分辨光谱。从光谱参数和通量之间的相关性来看，我们发现振荡主要归因于四个观测值中有三分之三的黑体辐射区域的变化，而另一个观察结果则显示了与恒定发射区域的温度和通量相关的温度变化。尽管差异的原因尚不清楚，但它可能与来源的光谱状态有关，从颜色图中的硬色差异可以观察到。
We present phase-resolved spectroscopies based on Hilbert-Huang transform (HHT) for millihertz quasi-periodic oscillations (mHz QPOs) in 4U 1636-536. This ~8 mHz QPO can be detected approximately several thousand seconds before a type-I X-ray burst. It was interpreted as marginally stable burning on the neutron-star surface. In this study, we used HHT to analyze the data collected by XMM-Newton between 2007 and 2009. HHT is a powerful tool that enables us to obtain instantaneous frequency, amplitude and phase of non-stationary periodicity phenomena, such as QPOs. With well-defined phases, the oscillation profile of the ~8 mHz QPO for 4U 1636-53 can be precisely revealed. In addition to the oscillation profile, phase-resolved spectra for the complete cycle are constructed. From the correlation between spectral parameters and fluxes, we find that the oscillation is mainly attributed to the variations of emitting area of blackbody radiation in three out of four observations with mHz QPO detections whereas the other one shows concurrent variation of temperature and flux with a constant emitting area. Although the cause of the difference is not clear, it might be related to the spectral state of the source that can be observed from hard color difference in color-color diagram.
