Are LIGO's Black Holes Made from Smaller Black Holes?

  title={Are LIGO's Black Holes Made from Smaller Black Holes?},
  author={Maya Fishbach and Daniel E. Holz and Benjamin Farr},
  journal={Bulletin of the American Physical Society},
One proposed formation channel for stellar mass black holes (BHs) is through hierarchical mergers of smaller BHs. Repeated mergers between comparable mass BHs leave an imprint on the spin of the resulting BH since the final BH spin is largely determined by the orbital angular momentum of the binary. We find that for stellar mass BHs forming hierarchically the distribution of spin magnitudes is universal, with a peak at and little support below . We show that the spin distribution is robust… 

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