标题： 使用希尔伯特-黄变换表征XTE J1550-564中4赫兹准周期振荡的间歇性 显示英文标题

标题： Characterizing Intermittency of 4-Hz Quasi-periodic Oscillation in XTE J1550-564 using Hilbert-Huang Transform

摘要： 我们基于希尔伯特-黄变换（HHT）展示了围绕黑洞X射线双星XTE J1550-564的4赫兹低频准周期振荡（LFQPO）演化的时频分析结果。LFQPO的起源仍然存在争议。为了理解峰展宽的原因，我们利用了一种新开发的时频分析方法HHT，以跟踪来自XTE J1550 564的4赫兹LFQPO的演化。通过自适应地从光变曲线中分解出约4赫兹的振荡成分并获取其瞬时频率，希尔伯特谱表明LFQPO由一系列在3赫兹和5赫兹之间偶尔出现的间歇性振荡组成。我们进一步通过计算间歇性振荡的瞬时振幅的置信限来表征这种间歇性，并构建了QPO的高振幅和低振幅持续时间的分布，这些是具有和不具有显著~4赫兹振荡的时间间隔。平均高振幅持续时间为1.45秒，90%的振荡段的寿命低于3.1秒。平均低振幅持续时间为0.42秒，其中90%的段短于0.73秒。此外，这些间歇性振荡表现出振荡的均方根振幅与平均计数率之间的相关性。这种相关性可能类似于通过傅里叶分析在4赫兹LFQPO中发现的线性均方根-流量关系。我们得出结论，功率谱中的LFQPO峰展宽是由于具有不同频率的间歇性振荡造成的，这可以通过使用Lense-Thirring进动模型来解释。 显示英文摘要

摘要： We present the time-frequency analysis results based on the Hilbert-Huang transform (HHT) for the evolution of a 4-Hz low-frequency quasi-periodic oscillation (LFQPO) around the black hole X-ray binary XTE J1550-564. The origin of LFQPOs is still debated. To understand the cause of the peak broadening, we utilized a recently developed time-frequency analysis, HHT, for tracking the evolution of the 4-Hz LFQPO from XTE J1550 564. By adaptively decomposing the ~4-Hz oscillatory component from the light curve and acquiring its instantaneous frequency, the Hilbert spectrum illustrates that the LFQPO is composed of a series of intermittent oscillations appearing occasionally between 3 Hz and 5 Hz. We further characterized this intermittency by computing the confidence limits of the instantaneous amplitudes of the intermittent oscillations, and constructed both the distributions of the QPO's high and low amplitude durations, which are the time intervals with and without significant ~4-Hz oscillations, respectively. The mean high amplitude duration is 1.45 s and 90% of the oscillation segments have lifetimes below 3.1 s. The mean low amplitude duration is 0.42 s and 90% of these segments are shorter than 0.73 s. In addition, these intermittent oscillations exhibit a correlation between the oscillation's rms amplitude and mean count rate. This correlation could be analogous to the linear rms-flux relation found in the 4-Hz LFQPO through Fourier analysis. We conclude that the LFQPO peak in the power spectrum is broadened owing to intermittent oscillations with varying frequencies, which could be explained by using the Lense-Thirring precession model.