# The impact of pair-instability mass loss on the binary black hole mass distribution

## TL;DR

This paper explores how pair-instability supernovae influence the maximum mass of black holes in binary systems, using population synthesis models to match observed gravitational wave data and predict future observational signatures.

## Contribution

It introduces a population synthesis model incorporating PPISNe and PISNe effects, predicting a maximum black hole mass of 40 solar masses and estimating merger fractions involving these phenomena.

## Key findings

- Maximum black hole mass predicted is 40 M_
- Approximately 10% of mergers involve a PPISN-processed black hole
- Predicted rates of PPISNe and PISNe increase with redshift up to z=2

## Abstract

A population of binary black hole mergers has now been observed in gravitational waves by Advanced LIGO and Virgo. The masses of these black holes appear to show evidence for a pile-up between $30$--$45$ $M_\odot$ and a cut-off above $\sim 45$ $M_\odot$. One possible explanation for such a pile-up and subsequent cut-off are pulsational pair-instability supernovae (PPISNe) and pair-instability supernovae (PISNe) in massive stars. We investigate the plausibility of this explanation in the context of isolated massive binaries. We study a population of massive binaries using the rapid population synthesis software COMPAS, incorporating models for PPISNe and PISNe. Our models predict a maximum black hole mass of $40$ $M_\odot$. We expect $\sim 10$\% of all binary black hole mergers at redshift z = 0 will include at least one component that went through a PPISN (with mass $30$--$40$ $M_\odot$), constituting $\sim 20$--$50$\% of binary black hole mergers observed during the first two observing runs of Advanced LIGO and Virgo. Empirical models based on fitting the gravitational-wave mass measurements to a combination of a power law and a Gaussian find a fraction too large to be associated with PPISNe in our models. The rates of PPISNe and PISNe track the low metallicity star formation rate, increasing out to redshift $z = 2$. These predictions may be tested both with future gravitational-wave observations and with observations of superluminous supernovae.