Eccentric binary blackhole mergers: The transition from inspiral to plunge in general relativity
Abstract
We study the transition from inspiral to plunge in general relativity by computing gravitational waveforms of nonspinning, equalmass blackhole binaries. We consider three sequences of simulations, starting with a quasicircular inspiral completing 1.5, 2.3 and 9.6 orbits, respectively, prior to coalescence of the holes. For each sequence, the binding energy of the system is kept constant and the orbital angular momentum is progressively reduced, producing orbits of increasing eccentricity and eventually a headon collision. We analyze in detail the radiation of energy and angular momentum in gravitational waves, the contribution of different multipolar components and the final spin of the remnant, comparing numerical predictions with the postNewtonian approximation and with extrapolations of pointparticle results. We find that the motion transitions from inspiral to plunge when the orbital angular momentum L=L_{crit}≃0.8M^{2}. For L<L_{crit} the radiated energy drops very rapidly. Orbits with L≃L_{crit} produce our largest dimensionless Kerr parameter for the remnant, j=J/M^{2}≃0.724±0.13 (to be compared with the Kerr parameter j≃0.69 resulting from quasicircular inspirals). This value is in good agreement with the value of 0.72 reported in [I. Hinder, B. Vaishnav, F. Herrmann, D. Shoemaker, and P. Laguna, Phys. Rev. D 77, 081502 (2008).PRVDAQ0556282110.1103/PhysRevD.77.081502]. These conclusions are quite insensitive to the initial separation of the holes, and they can be understood by extrapolating pointparticle results. Generalizing a model recently proposed by Buonanno, Kidder and Lehner [A. Buonanno, L. E. Kidder, and L. Lehner, Phys. Rev. D 77, 026004 (2008).PRVDAQ0556282110.1103/PhysRevD.77.026004] to eccentric binaries, we conjecture that (1) j≃0.724 is close to the maximal Kerr parameter that can be obtained by any merger of nonspinning holes, and (2) no binary merger (even if the binary members are extremal Kerr black holes with spins aligned to the orbital angular momentum, and the inspiral is highly eccentric) can violate the cosmic censorship conjecture.
 Publication:

Physical Review D
 Pub Date:
 September 2008
 DOI:
 10.1103/PhysRevD.78.064069
 arXiv:
 arXiv:0710.3823
 Bibcode:
 2008PhRvD..78f4069S
 Keywords:

 04.25.dg;
 04.25.Nx;
 04.30.Db;
 04.70.Bw;
 Numerical studies of black holes and blackhole binaries;
 PostNewtonian approximation;
 perturbation theory;
 related approximations;
 Wave generation and sources;
 Classical black holes;
 General Relativity and Quantum Cosmology;
 Astrophysics;
 High Energy Physics  Theory
 EPrint:
 Added sequence of long inspirals to the study. To match published version