A theoretical scenario for Galactic RR Lyrae in the Gaia database: constraints on the parallax offset

TL;DR

This paper uses advanced pulsation models to generate theoretical light curves and Period-Wesenheit relations for Galactic RR Lyrae stars in Gaia bands, enabling precise parallax estimates and constraining Gaia's parallax offset.

Contribution

It provides the first theoretical Gaia-band light curves and Period-Wesenheit relations for RR Lyrae, improving distance estimates and constraining Gaia's parallax zero-point offset.

Findings

Theoretical light curves and Wesenheit relations for RR Lyrae in Gaia bands are derived.

Predicted parallaxes agree with Gaia data assuming a negligible offset.

Results suggest Gaia's parallax zero-point offset is consistent with zero.

Abstract

On the basis of an extended set of nonlinear convective RR Lyrae pulsation models we derive the first theoretical light curves in the Gaia bands and the corresponding intensity-weighted mean magnitudes and pulsation amplitudes. The effects of chemical com-position on the derived Bailey diagrams in the Gaia filters are discussed for both Fundamental and First Overtone mode pulsators. The inferred mean magnitudes and colors are used to derive the first theoretical Period-Wesenheit relations for RR Lyrae in the Gaia filters. The application of the theoretical Period-Wesenheit relations for both the Fundamental and FirstOvertone mode to Galactic RR Lyrae in the Gaia Data Release 2 database and complementary information on individual metal abundances, allows us to derive theoretical estimates of their individual parallaxes. These results are compared with the astrometric solutions to conclude that a very small offset, consistent with zero, is required in order to reconcile the predicted distances with Gaia results.