吸积盘随机振荡光度功率谱密度中低频准周期振荡现象的研究

采用含有频率涨落噪声和指数形式关联随机力作用的广义朗之万(Langevin)方程模型描述黑洞吸积盘的垂向振荡,推导出吸积盘随机振荡光度功率谱密度的解析表达式,并讨论了系统参数对功率谱密度中低频准周期振荡(Low Frequency Quasi-Periodic Oscillations,LFQPOs)现象的影响。研究结果发现选取合适的系统参数时,功率谱密度曲线上出现了一个基频和一个二次谐频的共振双峰低频准周期振荡,基频峰对应的中心频率为吸积盘振荡的特征频率;随机力关联时间决定了基频峰的高度和宽度,频率噪声强度和粘滞阻尼只对二次谐频峰产生影响。结果说明吸积盘的随机振荡模型可以作为低频准周期振荡起源的一种解释。

Research on the Low Frequency Quasi-periodic Oscillations in Power Spectral Density of the Stochastic Oscillating Luminosity of Accretion Disk

In this paper,we improve the generalized Langevin equation model with fluctuating frequency and exponential function correlated stochastic force to describe the vertical oscillations of the accretion disk,then derive the analytical expression of the power spectrum density of stochastic oscillating luminosity,and discuss the influence of system parameters on low frequency quasi-periodic oscillations(LFQPOs)in power density spectrum.The results show that,for appropriate parameters,the double-peaked LFQPOs with a fundamental peak and a second harmonic peak can be found in the PSD curves,and the central frequency of primary peak corresponds to the characteristic frequency of accretion disk oscillationν0.Moreover,the correlation time of stochastic force determines the height and width of the primary peak,and frequency noise intensity and viscous coefficient only influence the second harmonic peak.These results confirm that the stochastic oscillation model of accretion disk should be an alternative interpretation for the origin of LFQPOs.