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首页> 外文期刊>PASJ: Publications of the Astronomical Society of Japan >How does a secular instability grow in a hyperaccretion flow?
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How does a secular instability grow in a hyperaccretion flow?

机译：过度分泌流中的长期不稳定性如何增长？

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Hyperaccretion flows with mass accretion rates far above the Eddington rate have an N-shaped equilibrium curve on the Sigma-(M) over dot plane (with Sigma and (M) over dot being surface density and mass accretion rate, respectively). The accretion flow on the lower Sigma branch of the N-shape is optically thick, advection-dominated accretion flow, while that on the upper one is neutrino-dominated accretion flow. The middle branch has a negative slope on the Sigma-(M) over dot plane, meaning that the flow on this branch is secularly unstable. To investigate how the instability affects the flow structure and what observable signatures are produced, we study the time evolution of the unstable hyperaccretion flow in response to variable mass injection rates by solving the height-averaged equations for viscous accretion flows. When a transition occurs from the lower branch to the upper branch (or from the upper branch to the lower branch), the surface density rapidly increases (decreases) around that transition region, which induces locally enhanced mass flow (referred to as non-steady mass flow) into (out of) that region. We confirm that the non-steady flow can create a kind of disturbance and that it propagates over the whole disk. However, the non-steady mass flow is not strong enough to induce coherent transition over the whole disk, unless the mass injection rate varies with time. When the injection rate continuously changes, the neutrino luminosity varies intermittently, thus producing step-function-like light curves, as the radiation efficiency discontinuously changes every time the local transition occurs. The effects of changing the N-shape and possible observational consequences on the gamma-ray burst emission are briefly discussed.
机译：质量增长速率远高于爱丁顿速率的超增长流在点平面上的Sigma-（M）上具有N形平衡曲线（点上的Sigma和（M）分别是表面密度和质量增加率）。 N形下部Sigma分支上的吸积流是光学上较厚的，对流为主的吸积流，而上部的是中微子为主的吸积流。中间分支在点平面上的Sigma-（M）上具有负斜率，这意味着该分支上的流动长期不稳定。为了研究不稳定性如何影响流动结构以及产生了哪些可观察的信号，我们通过求解粘性吸积流的高度平均方程，研究了响应于不同质量注入速率的不稳定超积流的时间演化。当从下分支到上分支（或从上分支到下分支）发生过渡时，表面密度在该过渡区域附近迅速增加（减小），从而引起局部增强的质量流（称为不稳定）质量流量）流入（流出）该区域。我们确认非稳定流会产生一种干扰，并且会在整个磁盘上传播。但是，除非质量注入速率随时间变化，否则非稳定质量流的强度不足以在整个磁盘上引起相干过渡。当注入速率连续变化时，中微子的亮度会间歇性地变化，从而产生阶跃函数状的光曲线，因为每次发生局部跃迁时辐射效率都会不连续地变化。简要讨论了改变N形的影响以及可能的观测结果对伽马射线突发发射的影响。

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