Astrophysical implications of GW190412 as a remnant of a previous black-hole merger

Understand

Two of the dominant channels to produce merging stellar-mass black-hole binaries are believed to be the isolated evolution of binary stars in the field and dynamical formation in star clusters.

• The first reported black-hole binary event from the third LIGO/Virgo observing run (GW190412) is unusual in that it has unequal masses, nonzero effective spin, and nonzero primary spin at 90\% confidence interval.
• We show that this event should be exceedingly rare in the context of both the field and cluster formation scenarios.
• Interpreting GW190412 as a remnant of a previous black-hole merger provides a promising route to explain its features.