The effect of matter structure on the gravitational waveform

TL;DR

This paper investigates how matter distribution and accelerations in the universe distort gravitational wave signals from distant binaries, impacting parameter estimation for future detectors like LISA.

Contribution

It demonstrates that peculiar accelerations significantly affect gravitational waveform analysis, introducing biases in parameter estimation beyond cosmological effects.

Findings

Peculiar accelerations can dominate cosmological acceleration effects on signals.

Biases in mass and coalescence time estimations are introduced by matter structure.

Errors in arrival time estimation impact multi-band gravitational wave observations.

Abstract

Third generation ground-based interferometers as well as the planned space-based interferometer LISA are expected to detect a plethora of gravitational wave signals from coalescing binaries at cosmological distance. The emitted gravitational waves propagate in the expanding universe through the inhomogeneous distribution of matter. Here we show that the acceleration of the universe and the peculiar acceleration of the binary with respect to the observer distort the gravitational chirp signal from the simplest General Relativity prediction beyond a mere time independent rescaling of the chirp mass, affecting intrinsic parameter estimations for the binaries visible by LISA. We find that the effect due to the peculiar acceleration can be much larger than the one due to the universe acceleration. Moreover, peculiar accelerations can introduce a bias in the estimation of parameters such as the time of coalescence and the individual masses of the binary. An error in the estimation of the arrival time will have an impact in the case of sources visible first by LISA and later by ground based interferometers.