Multi-messenger detection of black hole binaries in dark matter spikes

TL;DR

This paper explores how gravitational wave signals from black hole binaries in galactic centers can be combined with gamma-ray observations to indirectly study dark matter properties within dense spikes around supermassive black holes.

Contribution

It introduces a novel multi-messenger approach linking gravitational wave and gamma-ray signals to probe dark matter density profiles in galactic nuclei.

Findings

Dark matter spike self-annihilation luminosity decreases by up to 90%.

Binary interaction alters dark matter density, affecting gamma-ray flux.

Potential to indirectly detect dark matter through combined gravitational and gamma-ray signals.

Abstract

We investigate the inspiral of a high mass-ratio black hole binary located in the nucleus of a galaxy, where the primary central black hole is surrounded by a dense dark matter spike formed through accretion during the black hole growth phase. Within this spike, dark matter undergoes strong self-annihilation, producing a compact source of $\gamma$-ray radiation that is highly sensitive to spike density, while the binary emits gravitational waves at frequencies detectable by LISA. As the inspiralling binary interacts with the surrounding dark matter particles, it alters the density of the spike, thereby influencing the $\gamma$-ray flux from dark matter annihilation. We demonstrate that the spike self-annihilation luminosity decreases by $10\%$ to $90\%$ of its initial value, depending on the initial density profile and binary mass ratio, as the binary sweeps through the LISA band. This presents a new opportunity to indirectly probe dark matter through multi-messenger observations of galactic nuclei.