Simultaneous bounds on the gravitational dipole radiation and varying gravitational constant from compact binary inspirals

TL;DR

This paper investigates bounds on dipolar gravitational radiation and a varying gravitational constant using gravitational waves from binary inspirals, highlighting the importance of considering both effects simultaneously for accurate tests of gravity.

Contribution

It introduces a framework to simultaneously constrain dipolar gravitational radiation and varying G effects in binary inspiral waveforms using Fisher analysis.

Findings

Space-based detectors provide tighter bounds than ground-based detectors.

Constraints on dipolar radiation parameter B can reach <3×10^{-11}.

Constraints on G variation rate can reach <7×10^{-9} yr^{-1}.

Abstract

Compact binaries are an important class of gravitational-wave (GW) sources that can be detected by current and future GW observatories. They provide a testbed for general relativity (GR) in the highly dynamical strong-field regime. Here, we use GWs from inspiraling binary neutron stars and binary black holes to investigate dipolar gravitational radiation (DGR) and varying gravitational constant predicted by some alternative theories to GR, such as the scalar-tensor gravity. Within the parametrized post-Einsteinian framework, we introduce the parametrization of these two effects simultaneously into compact binaries' inspiral waveform and perform the Fisher-information-matrix analysis to estimate their simultaneous bounds. In general, the space-based GW detectors can give a tighter limit than ground-based ones. The tightest constraints can reach $\sigma_B<3\times10^{-11}$ for the DGR parameter $B$ and $\sigma_{\dot{G}}/G < 7\times10^{-9} \, {\rm yr}^{-1} $ for the varying $G$, when the time to coalescence of the GW event is close to the lifetime of space-based detectors. In addition, we analyze the correlation between these two effects and highlight the importance of considering both effects in order to arrive at more realistic results.