The model fitting of Gaia DR3 Classical Cepheid light and radial velocity curves

TL;DR

This study uses Gaia DR3 data and non-linear pulsation models to estimate Cepheid parameters, test Gaia parallaxes, and analyze the period dependence of the p-factor, advancing understanding of stellar structure and distance calibration.

Contribution

It introduces a model-fitting approach for Gaia Cepheids that constrains their structural parameters and tests Gaia parallaxes without requiring additional offsets.

Findings

Distances agree with Gaia parallaxes without extra offset

Masses and luminosities align with models including overshooting, mass loss, or rotation

The p-factor is constant at 1.22 +/- 0.05, with no period dependence

Abstract

Classical Cepheids are key astrophysical laboratories for studying stellar structure and evolution, and for calibrating the cosmic distance scale. Despite major progress, uncertainties remain regarding their masses, luminosities, distances, and the role of processes like core overshooting, rotation, and mass loss. The high-precision data from ESA Gaia's third data release offer an opportunity to address these issues. This study aims to estimate the structural parameters and distances of a sample of Classical Cepheids using non-linear convective pulsation models. It also tests the consistency of Gaia parallaxes, constrains the Mass Luminosity relation, and investigates the dependence of the projection factor (p-factor) on pulsation period. We analysed 46 Cepheids with precise Gaia DR3 photometry and radial velocities. Model fitting was performed by comparing predicted and observed light curves in Gaia G, GBP, and GRP bands, and radial velocity curves. Distances from the models were compared with Gaia parallaxes, including published corrections. Predicted masses and luminosities were used to constrain the ML relation; radial velocities allowed independent pfactor estimates. Distances show statistical agreement with Gaia parallaxes, requiring no additional global offset. Inferred masses and luminosities are consistent with evolution models including mild core overshooting, mass loss, or rotation. No significant period dependence of the pfactor is found, with a constant value of p = 1.22+/-0.05, consistent with recent studies. Results also agree with the Period-Wesenheit-Metallicity relation from Gaia DR3.