Relative origins of the low-mass BBH peak

Determine the relative contributions of supernova compactness structure and stable mass-transfer selection effects to the approximately 9–10-solar-mass peak in the binary-black-hole mass function.

Background

Two principal explanations are discussed for the global binary-black-hole mass-function maximum near 9–10 solar masses. One attributes the feature to non-monotonic stellar compactness and the resulting explodability and remnant-mass structure; the other attributes it to a lower-mass boundary imposed by stable mass transfer. Other channels may contribute, and the relative importance of the leading mechanisms is not yet established.

References

Most likely both mechanisms contribute, and their relative importance remains an open question: compactness alone does not account for the full drop in rate between $\sim10M$ and $\sim15M$ , and the most recent works combine compactness peaks with formation-channel components .

— The School on Gravity: from motion to commotion  (2610.13514 - Cardoso et al., 9 Oct 2026) in Chapter 1, Section 1.4.3, subsection “The global peak of the BBH mass function”