Scalar-tensor mixed polarization search of gravitational waves

TL;DR

This paper conducts a direct search for scalar-tensor mixed polarization modes in gravitational waves from compact binary mergers, providing the tightest constraints on scalar amplitudes in strong gravity regimes prior to merger.

Contribution

It presents the first direct search for scalar-tensor mixed polarization modes in gravitational waves from real merger events, setting new constraints on scalar amplitudes.

Findings

Constraints on scalar-mode amplitude ratio: ≤ 0.20 for GW170814

Constraints on scalar-mode amplitude ratio: ≤ 0.068 for GW170817

Tightest bounds on scalar amplitude before merger in strong gravity regimes

Abstract

An additional scalar degree of freedom for a gravitational wave is often predicted in theories of gravity beyond general relativity and can be used for a model-agnostic test of gravity. In this letter, we report the direct search for the scalar-tensor mixed polarization modes of gravitational waves from compact binaries in a strong regime of gravity by analyzing the data of GW170814 and GW170817, which are the merger events of binary black holes and binary neutron stars, respectively. Consequently, we obtain the constraints on the ratio of scalar-mode amplitude to tensor-mode amplitude: $\lesssim 0.20$ for GW170814 and $\lesssim 0.068$ for GW170817, which are the tightest constraints on the scalar amplitude in a strong regime of gravity before merger.