High mass but low spin: an exclusion region to rule out hierarchical black-hole mergers as a mechanism to populate the pair-instability mass gap

Understand

The occurrence of pair-instability supernovae is predicted to prevent the formation of black holes with masses $\gtrsim 50 M_\odot$.

• Recent gravitational-wave detections in this mass range require an explanation beyond that of standard stellar collapse.
• Current modeling strategies include the hierarchical assembly of previous generations of black-hole mergers as well as other mechanisms of astrophysical nature (lowered nuclear-reaction rates, envelope retention, stellar mergers, accretion, dredge-up episodes).
• In this paper, we point out the occurrence of an exclusion region that cannot be easily populated by hierarchical black-hole mergers.