Black hole induced spins from hyperbolic encounters in dense clusters
EntityUAM. Departamento de Física Teórica
10.1016/j.dark.2021.100882Physics of the Dark Universe 34 (2021): 100882
Funded byWe would like to thank Zachariah Etienne and Patrick E. Nelson for their help regarding BH hyperbolic encounters with the Einstein Toolkit. All the simulations have been run in the Hydra HPC cluster in the IFT. S.J. is supported by a predoctoral contract by the Spanish Ministry of Science, Ref. SEV-2016-0597- 19-2. The authors acknowledge support from the Research Project PGC2018-094773-B-C32 [MINECO, Spain-FEDER, Spain], and the Centro de Excelencia Severo Ochoa Program, Spain SEV-2016-0597
ProjectGobierno de España. PGC2018-094773-B-C32; Gobierno de España. SEV-2016-0597
SubjectsBlack holes; Gravitational waves; Física
Rights© 2021 The Authors
Esta obra está bajo una licencia de Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0 Internacional.
The black holes that have been detected via gravitational waves (GW) can have either astrophysical or primordial origin. Some GW events show significant spin for one of the components and have been assumed to be astrophysical, since primordial black holes are generated with very low spins. However, it is worth studying if they can increase their spin throughout the evolution of the universe. Possible mechanisms that have already been explored are via multiple black hole mergers and gas accretion. We propose here a new mechanism that can occur in dense clusters of black holes: the spin up of primordial black holes when they are involved in close hyperbolic encounters. We explore this effect numerically with the Einstein Toolkit for different initial conditions, including variable mass ratios. For equal masses, there is a maximum spin that can be induced on the black holes, ꭕ=a/m≤0.2. We find however that for large mass ratios one can attain spins up to ꭕ≃0.7, where the highest spin is induced on the most massive black hole. For small induced spins we provide simple analytical expressions that depend on the relative velocity and impact parameter
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