Bounding the mass of the graviton with gravitational waves: Effect of spin precessions in massive black hole binaries

TL;DR

This paper demonstrates that spin precessions in massive black hole binaries improve gravitational wave parameter estimation, enabling tighter bounds on the graviton mass using space-based detectors like LISA.

Contribution

It shows that spin precessions help break parameter degeneracies, restoring graviton mass bounds to levels comparable to non-spinning cases in gravitational wave observations.

Findings

Precessions enhance waveform modulations.

Graviton Compton wavelength bounds reach ~5 x 10^{16} km.

Precessions improve parameter estimation accuracy.

Abstract

Observations of gravitational waves from massive binary black hole systems at cosmological distances can be used to search for a dependence of the speed of propagation of the waves on wavelength, and thereby to bound the mass of a hypothetical graviton. We study the effects of precessions of the spins of the black holes and of the orbital angular momentum on the process of parameter estimation using matched filtering of gravitational-wave signals vs. theoretical template waveforms. For the proposed space interferometer LISA, we show that precessions, and the accompanying modulations of the gravitational waveforms, are effective in breaking degeneracies among the parameters being estimated, and effectively restore the achievable graviton-mass bounds to levels obtainable from binary inspirals without spin. For spinning, precessing binary black hole systems of equal masses (10^6 solar masses) at 3 Gpc, the bounds on the graviton Compton wavelength achievable are of the order of 5 X 10^{16} km.