Adiabatic evolution of asymmetric binaries on generic orbits with new fundamental fields I: characterization of gravitational wave fluxes

Abstract

We investigate the dynamics of asymmetric binaries in extensions of General Relativity featuring a massless scalar field non-minimally coupled to gravity, focusing on the interplay between eccentricity and inclination in fully generic bound orbits. Building on an effective field theory framework tailored to extreme- and intermediate-mass-ratio inspirals, we compute scalar-field perturbations using a new arbitrary-precision C++ code capable of evolving perturbations along generic Kerr geodesics, STORM. We investigate the complete set of scalar fluxes at infinity and through the horizon across the relevant parameter space and analyze their harmonic structure as a function of orbital geometry and black-hole spin. Our results advance ongoing efforts to construct accurate waveform models for asymmetric binaries beyond GR and lay the groundwork for precision tests of fundamental physics with next-generation gravitational-wave detectors.

Figures (18)

• Figure 1: Spectrum of the scalar energy (top panels) and angular momentum (bottom panels) fluxes emitted at the horizon (left panels) and at infinity (right panels) for the $(\ell,m)=(1,1)$ harmonic, corresponding to a binary configuration with $(a/M,e,p/M,\theta_{\rm inc})=(0.5,0.2,25,5^\circ)$. The central panel in each plot shows the mode contributions in the $(n,k)$ plane, with the color scale indicating the magnitude of the single-mode flux. The top (right) panels display the marginalized energy flux contributions, obtained for a given $k$ ($n$) by summing over the index $n$ ($k$).
• Figure 2: Bar plot of the energy (top panel) and angular momentum (bottom panel) fluxes at infinity and at the horizon, for scalar modes with different angular indices $(\ell,m)$, summed over the $(n,k)$ harmonics. Darker (lighter) shades denote modes with $\ell = m$ ($\ell \neq m$), respectively.
• Figure 3: Same as panels (a) and (b) of Fig. \ref{['fig:flux_horizon_infinity']}, but for $\theta_{\rm inc}=85^\circ$.
• Figure 4: Same as panels (a) and (b) of Fig. \ref{['fig:flux_horizon_infinity']}, but for $e = 0.8$.
• Figure 5: Spectrum of the scalar energy flux emitted at infinity for the $(\ell,m)=(1,1)$ harmonic. The binary parameters are $(e,p/M,\theta_{\rm inc})=(0.4,8,40^\circ)$. The left and right panels correspond to primary spins $a/M=0.1$ and $a/M=0.9$, respectively. The layout of the panels follows the same format as Fig. \ref{['fig:flux_horizon_infinity_ecc']}.