Gravitational Radiation from Coalescing Binary Neutron Stars. II : Simulations Including Back Reaction Potential : Astrophysics and Relativity

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We have performed numerical simulations of coalescence of binary neutron stars by a Newtonian hydrodynamics code including a back reaction potential expressed by the fifth time derivative of the quadrupole moments. To determine the fifth time derivatives of the quadrupole moments we solve two more Poisson equations for the first and the second time derivatives of the Newtonian gravitational potential. We use (x, y, z) coordinate with a typical number of grids 141×141×141. Simulations are started when two neutron stars just touch with each other. Each neutron star of mass 1.4 M_⊙ with γ=2 equation of state is spherically symmetric initially. It takes 〜80 hours CPU time by HITAC S820/80 to perform a simulation which is characterized by a non-dimensional orbital angular momentum q. We performed 2 simulations with different q. The radiated energy becomes 〜2 % of the rest mass. This corresponds to h〜10^<-21> with a few millisecond duration time for a hypothetical event at a distance of 10 Mpc. In the final stage all the matter seems to be inside the Schwarzschild radius. Since the value of q = a/m in the final stage is less than 0.3, the final destiny of the system will be a slowly rotating Kerr black hole.
理論物理学刊行会の論文
1989-12-25