Probing missing physics from inspiralling compact binaries via time-frequency tracks

Abstract

The orbital evolution of compact binary systems depends on the component masses and spins as well as the underlying theory of gravity. Because the orbital dynamics directly determine the frequency evolution of gravitational-wave signals, tracking this evolution provides a sensitive probe of general relativity (GR). We introduce a method that coherently stacks time-frequency pixel energies along the observed orbital-frequency trajectory while allowing controlled shifts along the frequency axis. The resulting stacked energy reveals a clear signature of the dominant quadrupole mode in GR. When an alternative theory of gravity is injected and analyzed with GR waveforms, the corresponding energy distribution in the time-frequency plane is markedly different. We use this behavior to formulate a new consistency test based on a normalized deviation between the observed signal and the posterior predictions from theoretical waveforms. Using waveforms in beyond-GR scenarios within the sensitivity of second-generation interferometers, we demonstrate the ability of this method to identify departures from GR. We also examine missing physics within GR itself by analyzing an eccentric binary and recovery with a quasi-circular model. Finally, we apply the method to GW190814 and find signatures consistent with higher-order multipoles.