Newtonian hydrodynamics of the coalescence of black holes with neutron stars - IV. Irrotational binaries with a soft equation of state

摘要: We present a numerical study of the hydrodynamics in final stages inspiral black hole–neutron star binary, when binary separation becomes comparable to stellar radius. use Newtonian three-dimensional Smooth Particle Hydrodynamics (SPH) code, and model neutron with stiff (adiabatic index Γ=3 2.5) polytropic equation state hole as point mass which accretes matter via an absorbing boundary at Schwarzschild Our initial conditions correspond irrotational binaries equilibrium (approximating compressible triaxial ellipsoid), we have explored configurations different values ratio qMNSMBH, ranging from q=0.5 0.2. The dynamical evolution is followed using ideal gas for approximately 23 ms. included gravitational radiation losses quadrupole approximation point-mass binary. For less case (Γ=3), find that after episode intense transfer, not completely disrupted remnant core remains orbit about stable configuration. Γ=2.5 – believed be appropriate nuclear densities tidal disruption process more complex, surviving transfer but being totally during second periastron passage. resulting accretion disc formed around contains few tenths solar mass. A nearly baryon-free axis system throughout coalescence, only modest beaming relativistic fireball could give rise gamma-ray burst would sufficient avoid excessive baryon contamination. some (of order 10−2 M⊙) may dynamically ejected system, thus contribute substantially amount observed r-process material galaxy. calculate waveforms luminosity emitted coalescence approximation, show they directly reflect morphology process. Finally, results simulations used spherical stars relaxed isolation conditions, gauge effect non-equilibrium on system.