Three-dimensional explosion dynamics of a critical-mass neutron star (in a binary)

Abstract

In a close neutron star binary resulting from the collapse of the rotating iron core of a collapsing supernova, the low-mass component of mass m undergoes explosive disruption at the final evolutionary stage of this binary. We have obtained a numerical solution for the three-dimensional dynamics of 0.1 M _⊙ iron ejecta with energy release 4.7 MeV per nucleon in the gravitational field of a massive neutron star with mass M. The numerical solution has been obtained by the method of particles, which is adequate for a collisionless description of the ejecta dynamics in the absence of an interstellar medium. As a test problem, the suggested model is compared with the well-known asymptotic solution (for m/M → 0), which we have also been able to slightly improve and extend. We analyze in detail the separation of the ejecta into two categories of particles with hyperbolic and elliptical orbits. We have been able to obtain a number of corollaries from the analytical solution. These have allowed us to estimate the kinetic energy of the ejecta as a function of the binary component mass ratio and the final pulsar velocity by applying the momentum conservation law in the pulsar—ejecta system. Further use of our calculations is promising for the formulation of initial conditions for the three-dimensional hydrodynamic problem of the collision of ejecta with presupernova shells, in particular, with the toroidal iron atmosphere obtained previously in our two-dimensional calculations of the collapse of a rotating stellar core.