Hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures

  title={Hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures},
  author={Davide Gerosa and Maya Fishbach},
  journal={Nature Astronomy},
We review theoretical findings, astrophysical modeling, and current gravitational-wave evidence of hierarchical stellar-mass black-hole mergers. While most of the compact binary mergers detected by LIGO and Virgo are expected to consist of firstgeneration black holes formed from the collapse of stars, others might instead be of second (or higher) generation, containing the remnants of previous black-hole mergers. Such a subpopulation of hierarchically assembled black holes presents distinctive… 
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