Dependence of Kilohertz Quasi-periodic Oscillation Properties on the Normal-Branch Oscillation Phase in Scorpius X-1
Dependence of Kilohertz Quasi-periodic Oscillation Properties on the Normal-Branch Oscillation Phase in Scorpius X-1
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DOI：
10.1086/323741
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发表时间：
2001-08
期刊：
影响因子：
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通讯作者：
Wenfei Yu;M. van der Klis;P. Jonker
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文献类型：
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作者：
Wenfei Yu;M. van der Klis;P. Jonker
我们分析了天蝎座X-1的Rossi X-Ray Timing Explorer数据，发现它同时存在千赫兹准周期振荡（QPOs）和~6-8赫兹正分支振荡（NBO）。利用0.03-0.5 s数据段的功率谱，我们发现上千赫兹QPO频率ν2和下千赫兹QPO振幅与上千赫兹QPO振幅之比都与NBO时间尺度上x射线计数率的变化呈反相关。频率依赖性与在更长的时间尺度上发现的相似（但可能弱于），但功率比依赖性与之相反。一个以NBO频率调制的圆盘材料上的辐射应力导致ν2变化的模型可以解释这些数据；这意味着NBO的一些通量变化来自内盘半径的内部。我们讨论了这些发现如何影响我们对千赫兹QPOs和低质量x射线双星的低频变异性的理解。
We analyzed Rossi X-Ray Timing Explorer data of Scorpius X-1, which show kilohertz quasi-periodic oscillations (QPOs) and the ~6-8 Hz normal-branch oscillation (NBO) simultaneously. Using power spectra of 0.03-0.5 s data segments, we find that both the upper kilohertz QPO frequency ν2 and the ratio of lower to upper kilohertz QPO amplitude are anticorrelated to variations in the X-ray count rate taking place on the NBO timescale. The frequency dependence is similar to (but probably weaker than) that found on longer timescales, but the power ratio dependence is opposite to it. A model where radiative stresses on the disk material, modulated at the NBO frequency, lead to changes in ν2 can explain the data; this implies that some of the NBO flux changes originate from inside the inner disk radius. We discuss how these findings affect our understanding of kilohertz QPOs and of the low-frequency variability of low-mass X-ray binaries.