Detection of LIGO-Virgo binary black holes in the pair-instability mass gap

Understand

By probing the population of binary black hole (BBH) mergers detected by LIGO-Virgo, we can infer properties about the underlying black hole formation channels.

• A mechanism known as pair-instability (PI) supernova is expected to prevent the formation of black holes from stellar collapse with mass greater than $\sim 40-65\,M_\odot$ and less than $\sim 120\,M_\odot$.
• Any BBH merger detected by LIGO-Virgo with a component black hole in this gap, known as the PI mass gap, likely originated from an alternative formation channel.
• Here, we firmly establish GW190521 as an outlier to the stellar-mass BBH population if the PI mass gap begins at or below $65\, M_{\odot}$.