Stellar binaries incident on supermassive black hole binaries: implications for double tidal disruption events, calcium-rich transients, and hypervelocity stars

TL;DR

This study investigates how stellar binaries interacting with supermassive black hole binaries can produce diverse phenomena like double tidal disruption events, hypervelocity stars, and gravitational-wave sources, with implications for various astrophysical transients.

Contribution

It provides a comprehensive analysis of stellar binary interactions with SMBHBs, revealing the probabilities of different outcomes including TDEs, mergers, and ejections, and explores their astrophysical implications.

Findings

Double TDEs occur at the percent level.

Ejected binaries have increased eccentricities.

Interaction enhances merger rates and gravitational-wave potential.

Abstract

We analyze the outcome of the interaction between a stellar binary and a supermassive black hole binary (SMBHB) by performing a large number of gravitational scattering experiments. Most of the encounters result in either the ejection of an intact binary or the ejection of two individual stars following the tidal breakup of the binary. However, tidal disruption events (TDEs) and mergers constitute a few percent of the outcomes, and double, temporally distinct TDEs (i.e., separated by at least one orbit of the supermassive black hole binary) occur at the percent level. We also demonstrate that the properties of the ejected binaries are significantly altered through the interaction with the SMBHB, and their large eccentricities increase the merger rate and could lead to gravitational-wave inspirals far from the nucleus of the host galaxy. We discuss our results in the context of observed tidal disruption events, hypervelocity stars, and remote supernovae, such as calcium-rich transients.