Detectability of compact intermediate-mass black hole binaries as low-frequency gravitational wave sources: the influence of dynamical friction of dark matter

TL;DR

This study explores how dark matter's dynamical friction influences the evolution and detectability of intermediate-mass black hole binaries as low-frequency gravitational wave sources, highlighting conditions that make them observable by LISA.

Contribution

It models the impact of dark matter dynamical friction on IMBH-MS binaries, expanding the parameter space for potential low-frequency GW sources detectable by LISA.

Findings

Dark matter dynamical friction drives binaries to low-frequency GW stages.

Binaries with specific donor masses and orbital periods can become LISA sources.

Dark matter effects extend the evolution timescale and parameter space.

Abstract

The black hole (BH) spin could significantly change the density of dark matter (DM) in its vicinity, creating a mini-spike of the density of DM. The dynamical friction (DF) between DM and the companion star of a BH can provide an efficient loss of angular momentum, driving the BH-main sequence (MS) star binary to evolve toward a compact orbit system. We investigate the influence of the DF of DM on the detectability of intermediate-mass black hole (IMBH)-MS binaries as low-frequency gravitational wave (GW) sources. Taking into account the DF of DM, we employ the detailed binary evolution code MESA to model the evolution of a large number of IMBH-MS binaries. Our simulation shows that the DF of DM can drive those IMBH-MS binaries to evolve toward low-frequency GW sources for a low donor-star mass, a high spike index, or a short initial orbital period. When the spike index $\gamma=1.60$, those IMBH-MS binaries with donor-star masses of $1.0-3.4~ M_{\odot}$ and initial orbital periods of $0.65-16.82~ \rm days$ could potentially evolve into visible LISA sources within a distance of $10~\rm kpc$. The DF of DM can enlarge the initial parameter space and prolong the bifurcation periods. In the low-frequency GW source stage, the X-ray luminosities of those IMBH X-ray binaries are $\sim 10^{35}-10^{36}~\rm erg\,s^{-1}$, hence they are ideal multimessenger objects.