Black-hole–neutron-star mergers resulting in the disruption of the neutron star and the formation of an accretion disk and/or the ejection of unbound material are prime candidates for the joint detection of gravitational-wave and electromagnetic signals when the next generation of gravitational-wave detectors comes online .
However , the disruption of the neutron star and the properties of the post-merger remnant are very sensitive to the parameters of the binary ( mass ratio , black hole spin , neutron star radius ) .
In this paper , we study the impact of the radius of the neutron star and the alignment of the black hole spin on black-hole–neutron-star mergers within the range of mass ratio currently deemed most likely for field binaries ( M _ { BH } \sim 7 M _ { NS } ) and for black hole spins large enough for the neutron star to disrupt ( J _ { BH } / M _ { BH } ^ { 2 } = 0.9 ) .
We find that : ( i ) In this regime , the merger is particularly sensitive to the radius of the neutron star , with remnant masses varying from 0.3 M _ { NS } to 0.1 M _ { NS } for changes of only 2 { km } in the NS radius ; ( ii ) 0.01 M _ { \odot } -0.05 M _ { \odot } of unbound material can be ejected with kinetic energy \mathrel { \raise 1.29 pt \hbox { $ > $ } \mkern - 14.0 mu \lower 2.58 pt \hbox { $ \sim$ } } 10 ^ { 51 % } { ergs } , a significant increase compared to low mass ratio , low spin binaries .
This ejecta could power detectable post-merger optical and radio afterglows .
( iii ) Only a small fraction of the Advanced LIGO events in this parameter range have gravitational-wave signals which could offer constraints on the equation of state of the neutron star ( at best \sim 3 \% of the events for a single detector at design sensitivity ) .
( iv ) A misaligned black hole spin works against disk formation , with less neutron star material remaining outside of the black hole after merger , and a larger fraction of that material remaining in the tidal tail instead of the forming accretion disk .
( v ) Large kicks v _ { kick } \mathrel { \raise 1.29 pt \hbox { $ > $ } \mkern - 14.0 mu \lower 2.58 pt \hbox { $% \sim$ } } 300 { km / s } can be given to the final black hole as a result of a precessing BHNS merger , when the disruption of the neutron star occurs just outside or within the innermost stable spherical orbit .