Disk Instability-Induced Hard-Soft Transition in Soft X-Ray Transients
Disk Instability-Induced Hard-Soft Transition in Soft X-Ray Transients
复制标题
软 X 射线瞬变中磁盘不稳定性引起的硬-软转变
DOI：
10.1093/pasj/48.1.93
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发表时间：
1996
影响因子：
2.3
通讯作者：
S. Mineshige
中科院分区：
文献类型：
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作者：
S. Mineshige
软X射线瞬变是黑洞候选者（BHC）在爆发期间表现出滞后的光谱跃迁;硬X射线峰值通常先于软X射线峰值。为了解释这种行为，我们提出了一个新的模型，其中磁盘的行为是不同的临界半径。由于氢和氦的部分电离，外部部分遭受热极限循环不稳定性，从而调制进入内部部分的质量流。然而，为了在静止期间产生弱X射线，应该在内部抑制不稳定性，这可能是由于光学深度小。相反，内部部分响应于来自外部部分的可变质量输入而在光学厚分支和光学薄分支之间经历强制双峰转变。在静止和上升阶段，内部位于光学薄的平流主导的分支上，从而产生硬幂律辐射，而在早期衰变阶段，内部位于光学厚的分支上，主要发射软辐射。我们的模型基本上可以解释黑洞瞬变的观测结果。
Soft X-ray transients that are black-hole candidates (BHCs) exhibit hysteretic spectral transitions during outbursts; hard X-ray peaks generally precede soft X-ray peaks. To account for such behavior we propose a new model, in which the disk behavior is distinct across a critical radius. The outer portions suffer a thermal limit-cycle instability owing to partial ionization of hydrogen and helium, thereby modulating mass flow into the inner portions. In order to produce weak X-rays during the quiescence, however, the instability should be suppressed in the inner portions, probably due to small optical depths. Instead, the inner portions undergo forced bimodal transitions between the optically thick and thin branches in response to variable mass input from the outer portions. The inner part is on the optically thin, advection-dominated branch in the quiescence and rise phases, thus producing hard power-law radiation, while it is on the optically thick branch in the early decay phase, predominantly emitting soft radiation. Our model can basically account for the observations of black-hole transients.