Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-radiation Hydrodynamics Study
Year: 2018
Type: article
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.
Source: The Astrophysical Journal
Authors: Sho Fujibayashi, Kenta Kiuchi, Nobuya Nishimura, Yuichiro Sekiguchi, Masaru Shibata
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: G1353019307, G1755930699, 中性子星合体におけるrプロセス元素合成と重力波対応天体, G2253600734, Gravitational waves and electromagnetic signals from the merger of neutron star binaries, Developement of Numerical Relativity neutrino Radiation MagnetoHydroDynamics code and its application to a central engine of short gamma-ray bursts, G294042113, G3728652323, G3734284000, G3828783607, G4074787749, G4570048345, Coalescence of compact binary and the origin of heavy elements, G5237506172, Numerical modeling of the central engine of short gamma-ray bursts, G6068824168, G6667447657, G7677962413, G7768269416, G8078205377, G8138599175, G8157362042, Study of neutron star mergers by high cadence optical observations
OpenAlex ID: W2767870801