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Free keywords:
General Relativity and Quantum Cosmology, gr-qc
Abstract:
The early inspiral phase of a compact binary coalescence is well modelled by
the post-Newtonian (PN) approximation to the orbital energy and gravitational
wave flux. The transition from the inspiral phase to the plunge can be defined
by the minimum energy circular orbit (MECO). In the extreme mass-ratio limit,
up to the highest PN order known, the PN energy equals the energy of the exact
Kerr solution. However, for comparable-mass systems the MECO of the PN energy
does not exist when bodies have large spins. By including the exact Kerr limit
and recently published post-Newtonian terms we extract a well-defined minimum
of the orbital energy beyond which the plunge or merger occurs. We study the
hybrid condition for a number of cases of both black hole and neutron stars and
compare to other commonly employed definitions. Our method can be used for any
known order of the post-Newtonian series and enables the MECO condition to be
used to define the end of the inspiral phase for highly spinning, comparable
mass systems.
