论文标题
茧的突破并逃离中子星的射出
Cocoon breakout and escape from the ejecta of neutron star mergers
论文作者
论文摘要
茧是通过环境物质传播喷气的一种不可避免的产物，并占据了一小部分喷气能量。简而言之，环境物质是从中子恒星合并的弹射物，以高速$ \ sim 0.2 c $扩展，与Collapsars中的静态恒星信封相反。将2D相对论的流体动力模拟与射流密度曲线为$ρ\ propto r^{ - 2} $，我们发现扩展有很大的不同。只有0.5---5 \％的Cocoon质量逃脱（比）弹射器，开头$ 20^{\ circ} $ - $ 30^{\ circ} $，而它是$ \ sim 100 \％$ $，并且在折叠中球形。我们还分析地获得了逃避和捕获的茧的质量和能量的份额。由于逃脱的茧的质量很小，并且被困的茧被喷射和逃脱的茧掩盖，因此我们得出结论，不太可能将茧发射视为与重力波事件GW170817的对应物。
The cocoon is an inevitable product of a jet propagating through ambient matter, and takes a fair fraction of the jet energy. In short gamma-ray bursts, the ambient matter is the ejecta from the merger of neutron stars, expanding with a high velocity $\sim 0.2 c$, in contrast to the static stellar envelope in collapsars. Using 2D relativistic hydrodynamic simulations with the ejecta density profile as $ρ\propto r^{-2}$, we find that the expansion makes a big difference; only 0.5--5\% of the cocoon mass escapes from (faster than) the ejecta, with an opening angle $20^{\circ}$--$30^{\circ}$, while it is $\sim 100\%$ and spherical in collapsars. We also analytically obtain the shares of mass and energies for the escaped and trapped cocoons. Because the mass of the escaped cocoon is small and the trapped cocoon is concealed by the ejecta and the escaped cocoon, we conclude that it is unlikely that the cocoon emission was observed as a counterpart to the gravitational wave event GW170817.
