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GR: Fachverband Gravitation und Relativitätstheorie
GR 4: GW I
GR 4.1: Vortrag
Dienstag, 1. April 2025, 16:15–16:35, ZHG008
Predicting black-hole spins from hierarchical mergers of binary black holes — •Angela Borchers1,2, Claire Ye3, and Maya Fishbach3 — 1Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Callinstraße 38, 30167 Hannover, Germany — 2Leibniz Universität Hannover, Callinstraße 38, 30167 Hannover, Germany — 3Canadian Institute for Theoretical Astrophysics, 60 St George St, University of Toronto, Toronto, ON M5S 3H8, Canada
Stellar black holes often form binaries in dense stellar clusters. When these binaries merge, they produce remnant black holes, which, after some time, might find a black hole companion and merge again. We call these hierarchical mergers. Previous studies have shown that the spin distribution of black holes in hierarchical mergers peaks at 0.69, independent of the initial black hole spins and the merger generation. However, these mergers can produce recoil kick velocities large enough for remnants to be ejected from their clusters, which means they will not contribute to the black-hole spin distribution in the cluster. We have investigated what are the spins of black holes from hierarchical mergers when recoil kicks are considered. In this talk, I will show that the distribution of retained black holes is not identical to the distribution of all black holes. Besides, I will discuss how the distribution depends on the black-hole birth spins and the merger generation. Our results complement earlier studies in understanding the characteristics of black holes formed in hierarchical mergers, which is essential when identifying the formation origin of black holes from gravitational-wave observations.
Keywords: Black-hole binaries; Hierarchical mergers; Dense stellar clusters; Gravitational-wave observations