Polarization test of gravitational waves from compact binary coalescences

Abstract

Gravitational waves have only two polarization modes in general relativity. However, there are six possible modes of polarization in a generic metric theory of gravity. Thus, tests of gravitational-wave polarization can be tools for pursuing the nature of space-time structure. The observations of gravitational waves with a worldwide network of interferometric detectors such as Advanced LIGO, Advanced Virgo, and KAGRA will make it possible to obtain the information of gravitational-wave polarization from detector signals. We study the separability of the polarization modes for the inspiral gravitational waves from the compact binary coalescences systematically. Unlike some other waveforms such as burst, the binary parameters need to be properly considered. We show that three polarization modes of gravitational waves would be separable with the global network of three detectors to some extent, depending on the signal-to-noise ratio and the duration of the signal. We also show that with four detectors the three polarization modes would be more easily distinguished by breaking a degeneracy of the polarization modes and even the four polarization modes would be separable.