The Final State from Generic Binary Black Hole Coalescence: Mass, Spin, and Gravitational Recoil

Open Access
Healy, James
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
November 16, 2009
Committee Members:
  • Pablo Laguna, Dissertation Advisor
  • Lee S Finn, Committee Chair
  • Pablo Laguna, Committee Member
  • Martin Bojowald, Committee Member
  • Richard Alan Wade, Committee Member
  • Black Hole
  • Binary Black Holes
  • Numerical Relativity
  • Gravitational Waves
  • Final State
Since the breakthroughs of numerically solving Einstein's Equations of gravity in the early 21st century, numerical relativity has been used primarily to study the most astrophysically relevant binary black hole configuration, the quasi-circular inspiral. Various aspects of the quasi-circular system with different spin configurations have been studied, including the gravitational radiation and the final state of the spacetime, that is, its mass, spin, and recoil velocity (or kick). However, these quasi-circular configurations cover a small sliver of the parameter space of solutions for binary black hole spacetimes. This dissertation explores the final state from generic binary black hole coalescence, considering a broad range of initial orbital configurations, from direct plunges to escape and recapture events to quasi-circular inspirals and to even more energetic orbits. Gravitational recoil is caused by the anisotropic emission of gravitational radiation due to asymmetries in the initial binary black hole spacetime. For quasi-circular inspirals, the beamed radiation tends to average over the inspiral, with the main contribution coming from the plunge. By considering hyperbolic encounters that are plunge-dominated, we observe an enhancement of the preferential beaming leading to kick velocities of ~ 10,000 km/s for the sequence studied, about 2.5X larger than the highest projected kick from a quasi-circular configuration. Despite the higher magnitude kicks produced, these systems exhibit the same general dependence of the kick on the initial spin configurations as the quasi-circular system. The final spin of the system is determined by the residual orbital and spin angular momentum that is not radiated in the process of merging. Considering plunge-dominated systems with a broad range of initial spin configurations and impact angles provides a comprehensive search of those configurations that maximize the final spin of the remnant black hole. We estimate that the final spin can reach a maximum a/M_h ~ 0.992 for extremal spinning, equal-mass black hole mergers. In addition, we find that as one increases the orbital angular momentum, the mergers produce black holes with mass and spin oscillating around the values of a golden black hole. We find that the values of the parameters for the golden black hole correspond to the final state of the black hole obtained from the quasi-circular system with the same spin configuration. Lastly, we confirm that zoom-whirl behavior can survive the dissipatory drain of full General Relativity and is not confined to a finely tuned region of initial parameters.