The interplay of disc wind and dynamical ejecta in the aftermath of neutron star-black hole mergers
The interplay of disc wind and dynamical ejecta in the aftermath of neutron star-black hole mergers
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DOI：
10.1093/mnras/stv238
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发表时间：
2015-05-01
影响因子：
4.8
通讯作者：
Rosswog, Stephan
中科院分区：
文献类型：
--
作者：
Fernandez, Rodrigo;Quataert, Eliot;Rosswog, Stephan
我们探索中子星和黑洞合并过程中产生的不同喷射物成分的演化。我们的重点是合并过程中动态喷射的物质与残余吸积盘在粘性时间尺度上发射的风之间的相互作用。这些组件预计会产生电磁瞬变并产生 r 过程元素，单独考虑时每个元素都具有不同的特征。在这里，我们介绍了一种两步方法，使用二维和三维流体动力学模拟来研究它们的组合演化。从合并模拟的输出开始，我们根据其相空间分布识别初始条件下的每个分量，并以轴对称方式演化吸积盘。从该圆盘吹出的风被注入三维计算域，动态喷射物在此演化。我们发现风可以在超过 100 毫秒的时间尺度上抑制后退吸积。由于自相似的粘性演化，晚期的盘吸积仍然接近幂律时间依赖性α t(-2.2)。这可以为一些后期伽马射线爆发引擎活动提供动力，尽管可用能量明显低于传统后备模型。由于 r 过程而包含放射性加热不会显着影响后退吸积率或盘风。我们没有发现由于与动力喷射物的相互作用而对大半径处的风特性有任何显着的改变。这是两个组件的膨胀速度不同的结果。
We explore the evolution of the different ejecta components generated during the merger of a neutron star and a black hole. Our focus is the interplay between material ejected dynamically during the merger, and the wind launched on a viscous time-scale by the remnant accretion disc. These components are expected to contribute to an electromagnetic transient and to produce r-process elements, each with a different signature when considered separately. Here we introduce a two-step approach to investigate their combined evolution, using two-and three-dimensional hydrodynamic simulations. Starting from the output of a merger simulation, we identify each component in the initial condition based on its phase-space distribution, and evolve the accretion disc in axisymmetry. The wind blown from this disc is injected into a three-dimensional computational domain where the dynamical ejecta is evolved. We find that the wind can suppress fallback accretion on time-scales longer than similar to 100 ms. Because of self-similar viscous evolution, the disc accretion at late times nevertheless approaches a power-law time dependence alpha t(-2.2). This can power some late-time gamma-ray burst engine activity, although the available energy is significantly less than in traditional fallback models. Inclusion of radioactive heating due to the r-process does not significantly affect the fallback accretion rate or the disc wind. We do not find any significant modification to the wind properties at large radius due to interaction with the dynamical ejecta. This is a consequence of the different expansion velocities of the two components.