Impact of a third body on binary neutron star tidal interactions

Abstract

To model a compact binary coalescence, it is commonly assumed that the binary evolves in isolation. In the present work, we relax this assumption by introducing a distant third body and investigating how the third body would affect the binary evolution. We treat this problem perturbatively and study tidal interaction in the binary due to the third body’s presence. We introduce appropriate modifications to the equations governing the orbital motions and the evolution equations of the binary component’s quadrupole moment. We compute the radiated energy and accumulated dephasing for the binary. Our findings indicate that for extreme-mass-ratio inspirals, these effects would not be significant. However, for binaries such as intermediate-mass-ratio inspirals, these effects are more relevant, and in some scenarios, the accumulated dephasing can reach up to 𝒪⁡(1) radians.