# New gravitational-wave data support a bimodal black-hole mass distribution

## TL;DR

This paper presents evidence from gravitational-wave data supporting a bimodal distribution of black-hole masses, which aligns with stellar evolution models and explains observed merger mass patterns.

## Contribution

It demonstrates that a bimodal black-hole mass model best reproduces the observed distribution of merging black hole masses in gravitational-wave data.

## Key findings

- Bimodal mass distribution explains observed chirp mass peaks.
- Only the bimodal model matches the structure of observed data.
- Other mass models fail to reproduce the observed distribution.

## Abstract

Detailed stellar evolution and supernova models yield a bimodal black-hole mass distribution with a narrow peak around 10 solar masses from stars within a narrow range of progenitor properties and a second broader peak starting around 20 solar masses from very massive progenitors. This bimodal black-hole mass distribution leads to a characteristic distribution of chirp masses of merging binary black holes, with two main peaks arising from the merger of two black holes where both come either from the low- or the high-mass peak and a smaller peak in between from the mixed merger of a low-mass and a high-mass black hole. We carry out a population synthesis study of binary black hole formation and compare the results to the observed chirp masses of gravitational-wave events. We find that only the bimodal black-hole mass prescription is able to reproduce the structure of peaks and gaps in the observed chirp-mass distribution, which is not matched by predictions from other remnant mass prescriptions in the literature.