TY - JOUR

T1 - Dynamical mass ejection from black hole-neutron star binaries

AU - Kyutoku, Koutarou

AU - Ioka, Kunihito

AU - Okawa, Hirotada

AU - Shibata, Masaru

AU - Taniguchi, Keisuke

N1 - Publisher Copyright:
© 2015 American Physical Society.

PY - 2015/8/18

Y1 - 2015/8/18

N2 - We investigate properties of material ejected dynamically in the merger of black hole-neutron star binaries by numerical-relativity simulations. We systematically study the dependence of ejecta properties on the mass ratio of the binary, spin of the black hole, and equation of state of the neutron-star matter. Dynamical mass ejection is driven primarily by tidal torque, and the ejecta is much more anisotropic than that from binary neutron star mergers. In particular, the dynamical ejecta is concentrated around the orbital plane with a half opening angle of 10°-20° and often sweeps out only a half of the plane. The ejecta mass can be as large as ∼0.1M, and the velocity is subrelativistic with ∼0.2-0.3c for typical cases. The ratio of the ejecta mass to the bound mass (disk and fallback components) is larger, and the ejecta velocity is larger, for larger values of the binary mass ratio, i.e., for larger values of the black-hole mass. The remnant black hole-disk system receives a kick velocity of O(100)kms-1 due to the ejecta linear momentum, and this easily dominates the kick velocity due to gravitational radiation. Structures of postmerger material, velocity distribution of the dynamical ejecta, fallback rates, and gravitational waves are also investigated. We also discuss the effect of ejecta anisotropy on electromagnetic counterparts, specifically a macronova/kilonova and synchrotron radio emission, developing analytic models.

AB - We investigate properties of material ejected dynamically in the merger of black hole-neutron star binaries by numerical-relativity simulations. We systematically study the dependence of ejecta properties on the mass ratio of the binary, spin of the black hole, and equation of state of the neutron-star matter. Dynamical mass ejection is driven primarily by tidal torque, and the ejecta is much more anisotropic than that from binary neutron star mergers. In particular, the dynamical ejecta is concentrated around the orbital plane with a half opening angle of 10°-20° and often sweeps out only a half of the plane. The ejecta mass can be as large as ∼0.1M, and the velocity is subrelativistic with ∼0.2-0.3c for typical cases. The ratio of the ejecta mass to the bound mass (disk and fallback components) is larger, and the ejecta velocity is larger, for larger values of the binary mass ratio, i.e., for larger values of the black-hole mass. The remnant black hole-disk system receives a kick velocity of O(100)kms-1 due to the ejecta linear momentum, and this easily dominates the kick velocity due to gravitational radiation. Structures of postmerger material, velocity distribution of the dynamical ejecta, fallback rates, and gravitational waves are also investigated. We also discuss the effect of ejecta anisotropy on electromagnetic counterparts, specifically a macronova/kilonova and synchrotron radio emission, developing analytic models.

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U2 - 10.1103/PhysRevD.92.044028

DO - 10.1103/PhysRevD.92.044028

M3 - Article

AN - SCOPUS:84940417385

VL - 92

JO - Physical Review D - Particles, Fields, Gravitation and Cosmology

JF - Physical Review D - Particles, Fields, Gravitation and Cosmology

SN - 1550-7998

IS - 4

M1 - 044028

ER -