Black Hole Gravitational Potential Enhanced Fallback Accretion onto the Nascent Lighter Compact Object: Tentative Evidence in the O3 Run Data of LIGO/Virgo

TL;DR

This paper investigates how the gravitational potential of a black hole can enhance fallback accretion onto a lighter compact object in binary systems, providing tentative observational evidence and proposing methods to test this correlation with future gravitational wave data.

Contribution

It presents the first analysis of mass correlation in low mass ratio binary black hole events and demonstrates the potential to detect such correlations with upcoming observations.

Findings

Tentative evidence for mass correlation in low mass ratio events.

Simulations show correlation detection is feasible with dozens of events.

Bayesian inference can robustly test the existence of mass correlation.

Abstract

In a binary system, the gravitational potential of the primary black hole may play an important role in enhancing the fallback accretion onto the lighter compact object newly formed in the second supernova explosion. As a result, the final masses of the binary compact objects would be correlated, as suggested recently by Safarzadeh \& Wysocki. In this work, we analyze the mass distribution of four gravitational-wave events, which are characterized by both a small mass ratio and a low mass ($\leq 5M_\odot$) of the light component, and find tentative evidence for a mass correlation among the objects. To evaluate the feasibility of testing such a hypothesis with upcoming observations, we carry out simulations with a mock population and perform Bayesian hierarchical inference for the mass distribution. We find that with dozens of low mass ratio events, whether there exists correlation in the component mass distributions or not can be robustly tested and the correlation, if it exists, can be well determined.