First search for nontensorial gravitational waves from known pulsars

TL;DR

This study conducts the first directed search for non-tensorial gravitational waves from known pulsars, testing for scalar, vector, and tensor modes without assuming a specific gravity theory, and sets new upper limits on non-tensorial strains.

Contribution

It introduces a method to detect non-tensorial gravitational waves from pulsars, providing the first upper limits on scalar and vector strains in a theory-independent manner.

Findings

No evidence of gravitational waves of any polarization was found.

Established upper limits for scalar and vector strains comparable to tensor strain limits.

Results can constrain alternative theories of gravity.

Abstract

We present results from the first directed search for nontensorial gravitational waves. While general relativity allows for tensorial (plus and cross) modes only, a generic metric theory may, in principle, predict waves with up to six different polarizations. This analysis is sensitive to continuous signals of scalar, vector or tensor polarizations, and does not rely on any specific theory of gravity. After searching data from the first observation run of the advanced LIGO detectors for signals at twice the rotational frequency of 200 known pulsars, we find no evidence of gravitational waves of any polarization. We report the first upper limits for scalar and vector strains, finding values comparable in magnitude to previously-published limits for tensor strain. Our results may be translated into constraints on specific alternative theories of gravity.