Viscous-dynamical Ejecta from Binary Neutron Star Mergers
Viscous-dynamical Ejecta from Binary Neutron Star Mergers
复制标题
DOI：
10.3847/2041-8213/aaf053
复制
发表时间：
2018-09
期刊：
影响因子：
--
通讯作者：
D. Radice;A. Perego;K. Hotokezaka;S. Bernuzzi;S. Fromm;L. Roberts
中科院分区：
文献类型：
--
作者：
D. Radice;A. Perego;K. Hotokezaka;S. Bernuzzi;S. Fromm;L. Roberts
具有粘性的双中子星合并的广义相对论模拟揭示了一种新的流出机制，该机制运行在动态时间尺度上的不等质量双子星中，并由湍流粘性实现。这些“粘性动力”喷射物是在合并期间发射的，这是由于次级星系和主星系之间的质量交换流的热化。它们的特征是速度渐近可达~ 0.8c，质量取决于粘性机制的效率。根据合并过程中由磁流体动力学不稳定性引起的有效粘度的未知强度，动态抛射物的总质量可能会增加几个因子，而抛射物的快尾质量（渐近速度≥0.6c）可能会增加多达四个数量级。膨胀的粘性动力抛射物的放射性衰变可以在第一个小时内产生具有自由中子衰变特征的明亮千新星瞬态，并在几天的时间尺度上增强近红外通量。喷射物与星际介质相互作用产生的同步加速器残余物也会因黏度的增加而显著增强。在GW170817的情况下，这样的残余物可以在未来几个月到几年内通过无线电信号的重新变亮而被探测到。
General-relativistic simulations of binary neutron star (NS) mergers with viscosity reveal a new outflow mechanism operating in unequal mass binaries on dynamical timescales and enabled by turbulent viscosity. These “viscous-dynamical” ejecta are launched during the merger due to the thermalization of mass exchange streams between the secondary and the primary NS. They are characterized by asymptotic velocities extending up to ∼0.8c, and have masses that depend on the efficiency of the viscous mechanism. Depending on the unknown strength of the effective viscosity arising from magnetohydrodynamic instabilities operating during the merger, the overall mass of the dynamical ejecta could be enhanced by a factor of a few and the mass of the fast tail of the ejecta, having asymptotic velocities ≥0.6c, by up to four orders of magnitude. The radioactive decay of the expanding viscous-dynamical ejecta could produce bright kilonova transients with signatures of free neutron decay in the first hour, and enhanced near-infrared flux on a timescale of a few days. The synchrotron remnant produced by the interaction between the ejecta and the interstellar medium could also be significantly enhanced by viscosity. Such a remnant could be detected in the case of GW170817 as a rebrightening of the radio signal in the next months to years.