Observability of gravitational waves excited by binary stars orbiting around a supermassive black hole by space-based gravitational wave observatory

TL;DR

This paper models gravitational waveforms from binary stars orbiting a supermassive black hole, highlighting higher frequency oscillations and the importance of gravito-electromagnetic effects for future space-based GW detection.

Contribution

It introduces detailed waveform calculations for B-EMRIs including higher order multipole moments and GEM effects, improving accuracy for space-based gravitational wave observations.

Findings

Higher frequency oscillations are prominent in B-EMRI waveforms.

GEM effects significantly influence waveform distinguishability.

Waveforms with GEM effects are detectable and distinguishable by space-based GW detectors.

Abstract

We produce the gravitational waveforms for the extreme mass ratio inspiral systems (EMRIs) of binary stars moving around central supermassive black hole (SBH), or called B-EMRIs. We calculate the external orbits of the binary stars via the commonly used Hamilton-Jacobi (HJ) approach, and calculate the internal orbits of the binary stars via Lagrangian approach. To improve accuracy we adopt the quadrupole-octupole expression of gravitational wave (GW) and study the contribution of radiation reaction. Compared to the waveforms of EMRIs, there are higher frequency oscillations superposed on the waveforms of B-EMRIs. We perform frequency spectrum analysis of the GW waveforms, and find that higher frequency signals give their prominency in the waveforms of B-EMRIs. To obtain high precise result for future observation of GWs from space-based detector, we take into account gravito-electromagnetic (GEM) force, and compare the waveforms of B-EMRIs with GEM effects against those of B-EMRIs without GEM effects and against those of EMRIs. The result of mismatch shows that the waveforms of B-EMRIs are credibly distinguishable by the space-based GW detectors when GEM force is considered.