Numerical Study of Spin and Mass Changes in Hyperbolic Black Hole Encounters
Researchers used numerical relativity simulations to study how black holes change spin and mass when they encounter each other in hyperbolic trajectories without merging. The study examined equal-mass black hole pairs with various initial spins and orbital configurations, finding that spin-up and mass-gain are largest near the threshold between scattering and merging. The findings provide insights into black hole dynamics in strong-field gravity and may inform understanding of black hole populations in dense stellar environments.
A new numerical relativity study investigates how spinning black holes gain mass and change their spin during close hyperbolic encounters—trajectories where they pass near each other but do not merge. The researchers simulated equal-mass black hole pairs with initial spins ranging from -0.7 to 0.7 (aligned or anti-aligned with orbital angular momentum) and varied incident angles and momenta. The simulations reveal that spin-up and mass-gain are typically largest in systems with incident angles near the scattering-merging threshold, high momenta, and negative initial spins. Notably, highly spinning black holes (initial spin 0.7) sometimes experience spin-down despite gaining angular momentum, because the mass increase is proportionally larger. Across all simulations, the maximum spin increase was 0.3 and the maximum mass increase was 15%. These results advance understanding of black hole dynamics in strong-field gravity regimes.
What's missing
The study does not discuss potential astrophysical implications or observational signatures of these spin and mass changes, nor does it compare results to analytical predictions or previous work on black hole scattering dynamics.
What different sources said
- arXiv astro-phCenter
Spin-up and mass-gain in hyperbolic encounters of spinning black holes
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