2017/11/30 by Sho Fujibayashi, Kenta Kiuchi, Nobuya Nishimura +2 · 246 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Binary number #Differential rotation #Ejecta #Gamma-ray bursts and supernovae #Neutrino #Neutron star #Nucleosynthesis #Pulsars and Gravitational Waves Research #Shock (circulatory) #Shock wave #Torus #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/aabafd
published in The Astrophysical Journal 860(1), 64 (IOP Publishing) · 21 pages, 18 figures, accepted for publication in ApJ
openalex created_date 2017/11/17 · arxiv created 2018/06/05 · openalex publication_date 2018/06/10 · arxiv updated 2018/06/27 · openalex updated_date 2026/08/06
Abstract We perform long-term general relativistic neutrino radiation hydrodynamics simulations (in axisymmetry) for a massive neutron star (MNS) surrounded by a torus, which is a canonical remnant formed after the binary neutron star merger. We take into account the effects of viscosity, which is likely to arise in the merger remnant due to magnetohydrodynamical turbulence. The viscous effect plays key roles for the mass ejection from the remnant in two phases of the evolution. In the first t ≲ 10 ms, a differential rotation state of the MNS is changed to a rigidly rotating state. A shock wave caused by the variation of its quasi-equilibrium state induces significant mass ejection of mass ∼(0.5–2.0) for the α -viscosity parameter of 0.01–0.04. For the longer-term evolution with ∼0.1–10 s, a significant fraction of the torus material is ejected. We find that the total mass of the viscosity-driven ejecta ( ) could dominate over that of the dynamical ejecta ( ). The electron fraction, Y e , of the ejecta is always high enough ( Y e ≳ 0.25) that this post-merger ejecta is lanthanide-poor; hence, the opacity of the ejecta is likely to be ∼10–100 times lower than that of the dynamical ejecta. This indicates that the electromagnetic signal from the ejecta would be rapidly evolving, bright, and blue if it is observed from a small viewing angle (≲45°) for which the effect of the dynamical ejecta is minor.