An imperfect double: probing the physical origin of the low-frequency quasi-periodic oscillation and its harmonic in black hole binaries
An imperfect double: probing the physical origin of the low-frequency quasi-periodic oscillation and its harmonic in black hole binaries
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DOI：
10.1093/mnras/stt2236
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发表时间：
2013-07
影响因子：
4.8
通讯作者：
M. Axelsson;C. Done;L. Hjalmarsdotter
中科院分区：
文献类型：
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作者：
M. Axelsson;C. Done;L. Hjalmarsdotter
我们提取了黑洞双星XTE J1550-564在爆发上升阶段的强低频准周期振荡（QPO）及其谐波谱。我们将这些频率分辨光谱与时间平均光谱和快速（<0.1 s）变化的光谱进行比较。时间平均辐射的光谱可用圆盘、康普顿上散射尾及其反射来描述。QPO谱与最快速变化的谱非常相似，这意味着它出现在气流的最内部区域。它几乎不包含可检测的圆盘，而且它的康普顿光谱通常比时间平均发射更硬，反射也更少。谐波也几乎不包含可检测的圆盘分量，但具有系统地比QPO更软的康普顿谱，甚至比时间平均发射中的康普顿尾更软。我们解释这些结果的上下文中的截断盘模型，其中的内盘是由热流取代。在这幅图中，QPO可以由整个热内流的垂直（Lense-Thirring）进动产生，它的谐波可以由热内流中康普顿散射的角度依赖性产生。我们扩展这些模型，包括分层的热流，使其更软（较低的光学深度），在更大的半径接近截断盘，和更硬（较高的光学深度）在最里面的部分的流的快速变化产生。不同的光学深度与半径产生不同的角度依赖性的康普顿辐射，加权的基本的内部部分的热流，和谐波的外部。这是第一个模型，可以解释的频谱QPO，其谐波，在一个自洽的几何。
We extract the spectra of the strong low-frequency quasi-periodic oscillation (QPO) and its harmonic during the rising phase of an outburst in the black hole binary XTE J1550-564. We compare these frequency-resolved spectra to the time-averaged spectrum and the spectrum of the rapid (<0.1 s) variability. The spectrum of the time-averaged emission can be described by a disc, a Compton upscattered tail and its reflection. The QPO spectrum is very similar to the spectrum of the most rapid variability, implying it arises in the innermost regions of the flow. It contains little detectable disc, and its Compton spectrum is generally harder and shows less reflection than in the time-averaged emission. The harmonic likewise contains little detectable disc component, but has a Compton spectrum which is systematically softer than the QPO, softer even than the Compton tail in the time-averaged emission. We interpret these results in the context of the truncated disc model, where the inner disc is replaced by a hot flow. The QPO can arise in this picture from vertical (Lense-Thirring) precession of the entire hot inner flow, and its harmonic can be produced by the angular dependence of Compton scattering within the hot flow. We extend these models to include stratification of the hot flow, so that it is softer (lower optical depth) at larger radii closer to the truncated disc, and harder (higher optical depth) in the innermost parts of the flow where the rapid variability is produced. The different optical depth with radius gives rise to different angular dependence of the Comptonized emission, weighting the fundamental to the inner parts of the hot flow, and the harmonic to the outer. This is the first model which can explain both the spectrum of the QPO, and its harmonic, in a self consistent geometry.