Variable-Frequency Quasi-periodic Oscillations from the Galactic Microquasar GRS 1915+105
Variable-Frequency Quasi-periodic Oscillations from the Galactic Microquasar GRS 1915+105
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DOI：
10.1086/311899
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发表时间：
1999-01
期刊：
影响因子：
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通讯作者：
C. Markwardt;J. Swank;R. Taam
中科院分区：
文献类型：
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作者：
C. Markwardt;J. Swank;R. Taam
研究表明，当星系微类星体GRS 1915+105处于耀斑状态时，其频率在1 ~ 15 Hz之间连续变化，呈准周期振荡（QPOs）。本文报道了同时在4 s间隔的能谱和功率密度谱的分析。光厚吸积盘加幂律模型能很好地拟合每个时间步长的能谱，而功率密度谱由变红噪声分量加变频QPO组成。两个光谱的特征彼此之间有很强的相关性。当幂律分量变得坚硬和强烈时，1-15 Hz qpo出现，并且它们本身具有与幂律分量一致的能谱（均方根幅值高达10%）。然而，振荡的频率与热盘组件的参数最显著地相关。QPO频率与磁盘x射线通量之间的相关性最为密切。这一事实表明，QPO的性质不仅仅是由圆盘或日冕决定的。
We show that the galactic microquasar GRS 1915+105 exhibits quasi-periodic oscillations (QPOs) whose frequency varies continuously from 1 to 15 Hz during spectrally hard dips when the source is in a flaring state. We report here analyses of simultaneous energy spectra and power density spectra at 4 s intervals. The energy spectrum is well fit at each time step by an optically thick accretion disk plus power-law model, while the power density spectrum consists of a varying red noise component plus the variable-frequency QPO. The features of both spectra are strongly correlated with one another. The 1-15 Hz QPOs appear when the power-law component becomes hard and intense and themselves have an energy spectrum consistent with the power-law component (with rms amplitudes as high as 10%). The frequency of the oscillations, however, is most strikingly correlated with the parameters of the thermal disk component. The tightest correlation is between QPO frequency and disk X-ray flux. This fact indicates that the properties of the QPO are not determined solely by a disk or solely by a corona.