标题： MAXI J1820+070中准周期振荡的希尔伯特-黄变换分析 显示英文标题

标题： Hilbert-Huang Transform analysis of quasi-periodic oscillations in MAXI J1820+070

摘要： 我们基于希尔伯特-黄变换（HHT）对在黑洞X射线双星MAXI J1820+070中观测到的低频准周期振荡（LFQPOs）的演化进行了时频分析。通过经验模态分解（EMD）方法，我们将QPO成分的光变曲线分解，并测量不同能段光子之间的固有相位滞后。我们发现QPO相位滞后为负（低能光子滞后于高能光子），同时滞后的绝对值随能量增加而增大。通过对QPO的光变曲线应用希尔伯特变换，我们进一步提取了QPO的瞬时频率和振幅。将这些结果与傅里叶分析的结果进行比较，我们发现QPO峰的展宽主要是由频率调制引起的。通过进一步分析，我们发现这些调制可能与宽带噪声有共同的物理起源，并可通过喷流的内部冲击模型很好地解释。 显示英文摘要

摘要： We present time-frequency analysis, based on the Hilbert-Huang transform (HHT), of the evolution on the low-frequency quasi-periodic oscillations (LFQPOs) observed in the black hole X-ray binary MAXI J1820+070. Through the empirical mode decomposition (EMD) method, we decompose the light curve of the QPO component and measure its intrinsic phase lag between photons from different energy bands. We find that the QPO phase lag is negative (low energy photons lag behind high energy photons), meanwhile the absolute value of the lag increases with energy. By applying the Hilbert transform to the light curve of the QPO, we further extract the instantaneous frequency and amplitude of the QPO. Compared these results with those from the Fourier analysis, we find that the broadening of the QPO peak is mainly caused by the frequency modulation. Through further analysis, we find that these modulations could share a common physical origin with the broad-band noise, and can be well explained by the internal shock model of the jet.