On the X-ray time lags in the black hole candidates
On the X-ray time lags in the black hole candidates
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DOI：
10.1046/j.1365-8711.2001.04769.x
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发表时间：
2001-03
期刊：
影响因子：
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通讯作者：
O.Kotov;E.Churazov;M.Gilfanov
中科院分区：
文献类型：
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作者：
O.Kotov;E.Churazov;M.Gilfanov
结果表明，天鹅座X-1中时间滞后的能量依赖性排除了标准反射分量对观测到的滞后的任何显著贡献。该结论在0.1 ~ 10hz频率范围内是有效的，该频率范围内检测到的时间滞后足够显著。事实上，数据暗示反射分量在相反的方向上工作，减少了反射分量贡献显著的能量处的滞后。我们认为，观测到的时间滞后对能量的对数依赖性可以理解为，在一个非常简单的现象学模型中，由于谱幂律指数的小变化。我们假设在距离致密物体一定距离的范围内存在一个光学薄的流/日冕，发出类似幂律的光谱。局部发射光谱的斜率是距离的函数，最内层区域发射的最硬光谱。如果在不同半径的吸积流中引入不同时间尺度的扰动，则由于扰动在扩散时间尺度上的向内传播，所观察到的x射线滞后自然出现。
It is shown that the energy dependence of the time lags in Cygnus X-1 excludes any significant contribution of the standard reflected component to the observed lags. The conclusion is valid in the 0.1–10 Hz frequency range where time lags have been detected with high enough significance. In fact the data hint that reflected component is working in opposite direction, reducing the lags at energies where contribution of the reflected component is significant. We argue that the observed logarithmic dependence of time lags on energy can be understood as due to the small variations of the spectrum power law index in a very simple phenomenological model. We assume that an optically thin flow/corona, emitting a power law like spectrum, is present at a range of distances from the compact object. The slope of the locally emitted spectrum is a function of distance with the hardest spectrum emitted in the innermost region. If perturbations with different time scales are introduced to the accretion flow at different radii the observed X–ray lags naturally appear due to the inward propagation of perturbations on the diffusion time scales.