Accreting black hole binaries change their properties during evolution, passing through two main luminous states, dominated by either hard or soft X-rays. In the hard state, steady compact jets emitting multiwavelength radiation are present. Those jets are usually observed in radio, and when resolved, their extent is ≲10¹⁵ cm. Then, during hard-to-soft transitions, powerful ejecta in the form of blobs appear. They are observed up to distances of ∼10¹⁸ cm, which are ≳1000 times larger than the extent of hard-state jets. On the other hand, estimates of the accretion rates during most luminous hard states and the hard-to-soft transitions are very similar, implying that maximum achievable powers of both types of jets are similar and cannot cause a huge difference in their propagation. Instead, we explain the difference in the propagation length by postulating that the ejecta consist of electron-ion plasmas, whereas the hard-state jets consist mostly of electron–positron pairs. The inertia of the ejecta are then much higher than those of compact jets, and the former are not readily stopped by ambient media. A related result is that the accretion flow during the hard state is of standard and normal evolution, while it is a magnetically arrested disk during transient ejections. The pairs in hard-state jets can be produced by collisions of photons of the hard spectrum emitted by hot accretion flows within the jet base. On the other hand, the X-ray spectra during the state transitions are relatively soft, and the same process produces much fewer pairs.

中文翻译：

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黑洞X射线双星中致密喷流和瞬态喷流传播距离差异的原因


吸积黑洞双星在演化过程中改变了它们的特性，经历了以硬X射线或软X射线为主的两个主要发光状态。在硬态下，存在发射多波长辐射的稳定紧凑射流。这些喷流通常在无线电中观察到，解析后其范围为 ≲10 ¹⁵ 厘米。然后，在从硬到软的转变过程中，会出现斑点形式的强力喷射物。它们的观测距离可达 ∼10 ¹⁸ cm，比硬态射流的范围大 ≳1000 倍。另一方面，对大多数发光硬态和硬到软转变期间的吸积率的估计非常相似，这意味着两种类型射流的最大可实现功率相似，并且不会在它们的传播中造成巨大差异。相反，我们通过假设喷射物由电子-离子等离子体组成，而硬态射流主要由电子-正电子对组成，来解释传播长度的差异。喷射物的惯性远高于紧凑射流的惯性，并且前者不易被周围介质阻止。一个相关的结果是，硬态期间的吸积流是标准且正常演化的，而瞬态喷射期间它是磁滞盘。硬态射流中的对可以通过射流底座内的热吸积流发射的硬光谱光子的碰撞产生。另一方面，状态转变期间的 X 射线光谱相对较软，并且相同的过程产生的对要少得多。