The relation between radio and X-ray luminosity of black hole binaries: affected by inner cool disks?
The relation between radio and X-ray luminosity of black hole binaries: affected by inner cool disks?
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DOI：
10.1051/0004-6361/201322423
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发表时间：
2014-01
影响因子：
6.5
通讯作者：
E. Meyer-Hofmeister;F. Meyer
中科院分区：
文献类型：
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作者：
E. Meyer-Hofmeister;F. Meyer
上下文对黑洞X射线双星GX 339-4和V404 Cygni的观测已经证明了在硬光谱状态下射电和X射线辐射之间存在很强的相关性;然而，现在发现越来越多的源，即所谓的“离群值”，其射电辐射明显低于已建立的“标准”关系。已经考虑了几种解释，但双轨制的存在尚未得到充分理解。目标。我们认为，在硬光谱状态下，气体从日冕重新凝聚成一个凉爽的，弱的内盘可以提供额外的软光子康普顿化，导致更高的X射线光度结合相当不变的无线电发射，这大概是跟踪质量吸积率。方法.作为一个例子，我们确定了需要多少额外的光度，由于光子从一个潜在的磁盘将需要解释的数据，从代表性的离群源H1743-322。结果从康普顿光谱的计算与没有光子从底层磁盘的比较中，我们发现，所需的额外的X射线光度在于以及从理论模型的吸积流获得的范围内。结论.在硬光谱状态下，来自弱冷内盘的额外光子的康普顿化产生的射电/X射线光度关系可以解释异常源的观测，特别是H1743-322的数据，它是观测最详细的源。两条轨道上是否存在弱的内盘可能表明伴星的磁场存在差异。这些可能影响有效粘度和导热性，因此也影响再冷凝过程。
Context. Observations of the black hole X-ray binaries GX 339-4 and V404 Cygni have brought evidence of a strong correlation between radio and X-ray emission during the hard spectral state; however, now more and more sources, the so-called “outliers”, are found with a radio emission noticeably below the established “standard” relation. Several explanations have already been considered, but the existence of dual tracks is not yet fully understood. Aims. We suggest that in the hard spectral state re-condensation of gas from the corona into a cool, weak inner disk can provide additional soft photons for Comptonization, leading to a higher X-ray luminosity in combination with rather unchanged radio emission, which presumably traces the mass accretion rate. Methods. As an example, we determined how much additional luminosity due to photons from an underlying disk would be needed to explain the data from the representative outlier source H1743-322. Results. From the comparison with calculations of Compton spectra with and without the photons from an underlying disk, we find that the required additional X-ray luminosity lies well in the range obtained from theoretical models of the accretion flow. Conclusions. The radio/X-ray luminosity relation resulting from Comptonization of additional photons from a weak, cool inner disk during the hard spectral state can explain the observations of the outlier sources, especially the data for H1743-322, the source with the most detailed observations. The existence or non-existence of weak inner disks on the two tracks might point to a difference in the magnetic fields of the companion stars. These could affect the effective viscosity and the thermal conductivity, hence also the re-condensation process.