Impact of the axion-like self-interactions in gravitational atoms for LISA

TL;DR

This paper investigates how axion-like self-interactions in gravitational atoms affect gravitational wave signals detectable by LISA, enabling constraints on particle properties without Standard Model couplings.

Contribution

It introduces a dynamical formation mechanism for gravitational atom halos and assesses LISA's ability to probe axion-like particles through gravitational wave observations.

Findings

LISA can distinguish waveforms affected by halos for SNRs less than 100.

Constraints on boson masses around 10^{-17} to 10^{-15} eV and decay constants up to 3.2×10^{12} GeV are possible.

Optimal particle parameter recovery occurs for specific halo densities and binary configurations.

Abstract

Ultralight bosons with self-interactions, such as axion-like particles, can form astrophysical Bose-Einstein condensates around stars or compact objects, often referred to as gravitational atoms. In this work, we adopt a recently proposed dynamical formation mechanism for these halos and estimate their impact on extreme- and intermediate-mass-ratio inspirals when present around the primary black hole. We show that, for signal-to-noise ratios $\lesssim 100$, LISA can distinguish gravitational waveforms from binaries embedded in such halo overdensities. Our analysis indicates that LISA can probe boson masses $m_\mathrm{dm}\sim10^{-17}$-$10^{-15}\,\mathrm{eV}$ and decay constants $f_a\sim10^{10}$-$3.2 \times 10^{12}\,\mathrm{GeV}$ using binaries with total masses $M\sim10^4$-$10^5\,M_\odot$, assuming conservative DM densities consistent with the central values of Navarro-Frenk-White profiles. Allowing for higher background densities and different extreme-mass-ratio configurations further extends the accessible parameter space. Moreover, we find that for a binary configuration with $M\sim10^4\,M_\odot$, $\rho_\mathrm{dm} = 10^3\,\mathrm{GeV/cm^3}$, and signal-to-noise ratio $\mathrm{SNR}\sim20$, a particle mass of $m_\mathrm{dm}\sim2.5\times10^{-16}\,\mathrm{eV}$ and decay constant $f_a\sim6.3\times10^{10}\,\mathrm{GeV}$ maximize the dephasing due to dynamical friction, enabling the recovery of the particle parameters at the percent level. These results demonstrate that LISA can place constraints on axion-like particle masses and self-interactions without requiring additional couplings to Standard Model fields.