Double black holes in open clusters and a highlight to their hierarchical mergers in nuclear clusters

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• Debatri Chattopadhyay, Cardiff University
• Friday 14 October 2022, 13:00-14:00
• Potter room/Zoom.

If you have a question about this talk, please contact Isobel Romero-Shaw.

In this talk, I will present a work that investigates the relationship between the global properties of star clusters and their double black hole (DBH) populations. For this study, the code NBODY6 is used to evolve a suite of star cluster models with an initial mass of _{O(1e4) Msun and varying initial parameters. This work concluded that cluster metallicity plays the most significant role in determining the lifespan of a cluster, while the initial half-mass radius is dominant in setting the rate of BH exchange interactions in the central cluster regions. It is also observed that the mass of interacting BHs, rather than how frequently their interactions with other BHs occur, is more crucial in the thermal expansion and eventual evaporation of the cluster. We formulate a novel approach to easily quantify the degree of BH-BH dynamical activity in each model. 12 in-cluster and three out-of-cluster (after ejection from the cluster) DBH mergers of different types across the eleven models are presented. It is noted that cluster initial density plays the most crucial role in determining the number of DBH mergers, with the potential hint of too-high stellar density preventing in-cluster BH mergers. I will also give a highlight of my ongoing research on the formation of intermediate mass black holes (}10e2-10e4 Msun) in nuclear clusters with initial masses of ~O(1e6-8)Msun. This work utilizes a semi-analytical fast code. Different initial cluster conditions are explored – from their masses, density, metallicity to how black holes are paired in the models. We find that cluster mass evolution and double black hole pairing prescriptions used form important determinants in the mass of the final intermediate mass black holes.

My other interests include: neutron stars, radio pulsars including black hole-pulsar binaries and millisecond pulsars, neutron stars in isolated binaries and star clusters, black hole triple systems, stellar black hole spins

This talk is part of the DAMTP Friday GR Seminar series.

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