The tidal disruption of neutron stars by black holes in close binaries

Abstract

The probability and implication of the formation of doubly compact binary systems from close massive binaries are examined. It is pointed out that mass transfer may greatly reduce the separations in these systems; their orbits can then completely decay because of gravitational radiation in a time less than the age of the universe, leading to collision of the components. A model for a black hole/neutron star collision is proposed. The trajectory followed by a neutron star is analyzed, and equations of hydrodynamics are derived which describe the neutron star in an inertial frame following this trajectory. The tidal force exerted by the black hole is incorporated in the equations. The results of the model are discussed. The amount of mass ejected from the neutron star in the collision is determined, and the possible shortcomings of the model are reviewed. A statistical estimate for the frequency of black hole/neutron star collisions is obtained, and possible implications for nucleosynthesis and antineutrino emission are discussed.