Gaia-like astrometry and gravitational waves

TL;DR

This paper explores how gravitational waves affect Gaia-like astrometric measurements, focusing on residual analysis, modeling light deflection, and proposing search strategies using vector spherical harmonics to detect gravitational wave signals.

Contribution

It introduces a detailed model for gravitational wave-induced light deflection, derives formulas for VSH expansion of signals, and discusses Gaia's potential sensitivity for gravitational wave detection.

Findings

Derived explicit formulas for VSH expansion of gravitational wave signals

Identified Gaia's potential sensitivity to certain gravitational wave sources

Outlined a search strategy for gravitational waves in astrometric data

Abstract

This paper discusses the effects of gravitational waves on high-accuracy astrometric observations such as those delivered by Gaia. Depending on the frequency of gravitational waves, two regimes for the influence of gravitational waves on astrometric data are identified: the regime when the effects of gravitational waves directly influence the derived proper motions of astrometric sources and the regime when those effects mostly appear in the residuals of the standard astrometric solution. The paper is focused on the second regime while the known results for the first regime are briefly summarized. The deflection of light due to a plane gravitational wave is then discussed. Starting from a model for the deflection we derive the corresponding partial derivatives and summarize some ideas for the search strategy of such signals in high-accuracy astrometric data. In order to reduce the dimensionality of the parameter space the use of vector spherical harmonics is suggested and explained. The explicit formulas for the VSH expansion of the astrometric signal of a plain gravitational wave are derived. Finally, potential sensitivity of Gaia astrometric data is discussed. Potential astrophysical sources of gravitational waves that can be interesting for astrometric detection are identified.