Failed supernovae as a natural explanation for the binary black hole mass distribution

TL;DR

This paper investigates whether failed supernovae can naturally explain the observed bimodal and trimodal mass distributions of binary black holes, suggesting it as a plausible hypothesis supported by simplified models and observational data.

Contribution

It introduces a remnant function based on stellar evolution simulations that accounts for failed supernovae and compares its predictions with observed black hole mass distributions.

Findings

Failed supernovae reduce type II SN rates by ~25%.

The remnant function produces a mass distribution similar to observations.

Failed SNe and black hole island are plausible explanations for the mass distribution features.

Abstract

The more gravitational wave sources are detected, the better the mass distribution of binary black holes (BBHs) becomes known. This stellar graveyard shows several features, including an apparent mass gap which makes the distribution bimodal. The observed chirp mass distribution, in turn, appears to be trimodal. We aim to investigate to which extend we can explain the observed mass distribution with stellar evolution, specifically with the hypothesis that the mass gap is caused by the difference between successful and failed supernovae (SNe). We pose a hypothetical remnant function, based on literature of stellar evolution simulations, which relates initial mass to remnant mass, includes a black hole island and produces a bimodal remnant distribution. Moreover, we look at observed type II SN rates in an attempt to detect the effect of failed SNe. Finally, using a simplified estimation of binary evolution, we determine the remnant distribution resulting from our remnant function and compare it to observation. We find that failed SNe lower type II SN rates by approximately 25%, but the inferred rate from SN surveys is not accurate enough to confirm this. Furthermore, our estimation based on the remnant function produces a mass distribution that matches the general shape of the observed distributions of individual as well as chirp masses. Based on our research, we conclude that the failed SNe mechanism and the presence of the black hole island are a natural hypothesis for explaining the individual BBH mass distribution and chirp mass distribution. However, for a more firm conclusion more detailed simulations are needed.