Adding electromagnetic birefringence to pulsar timing and astrometry to detect gravitational waves

TL;DR

This paper introduces a method combining electromagnetic birefringence with pulsar timing and astrometry to enhance detection of gravitational waves, including those from alternative theories, using a total-angular-momentum formalism.

Contribution

It extends the cross-correlation framework for gravitational wave detection to include astrometry and spin-1 waves, providing a more comprehensive approach.

Findings

Derived efficient cross-correlation expressions using total-angular-momentum formalism.

Extended the framework to include astrometric data and spin-1 gravitational waves.

Applicable to both general-relativistic spin-2 and alternative spin-1 gravitational waves.

Abstract

It was recently shown that the time variation of the polarization of electromagnetic waves from pulsars can be used, in cross-correlation with pulsar timing, to probe the chirality of an isotropic gravitational wave background. Here, we show that the expression for the cross-correlation is derived efficiently with the total-angular-momentum formalism and use this framework to extend the formulation to cross-correlation with astrometry. We do so for spin-1 gravitational waves (that may arise in alternative-gravity theories) as well as the general-relativistic spin-2 gravitational waves.