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

¹ INAF-OACN Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
² INAF-Osservatorio Astronomico d’Abruzzo, Via Maggini sn, 64100 Teramo, Italy
³ Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cinthia Edificio 6, I-80126 Napoli, Italy
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁵ Scuola Superiore Meridionale, Largo San Marcellino10, I-80138 Napoli, Italy

^⋆ Corresponding author: roberto.molinaro@inaf.it

Received: 22 January 2025
Accepted: 19 June 2025

Abstract

Context. Classical Cepheids are fundamental astrophysical laboratories for studying stellar structure and evolution, as well as for calibrating the cosmic distance scale. Despite significant progress in observational and theoretical studies, uncertainties remain regarding their masses, luminosities, and distances, as well as the role of processes such as core overshooting, rotation, and mass loss. The advent of high-precision data from Eurepan Space Agency (ESA) Gaia’s Data Release 3 (DR3) provides an opportunity to address these questions.

Aims. The primary aim of this study is to estimate the main structural parameters and distances of a sample of classical Cepheids using non-linear convective pulsational models. The work also seeks to test the consistency of Gaia parallaxes, independently constrain the mass–luminosity (ML) relation, and investigate the dependence of the projection factor (p-factor) on the pulsational period.

Methods. A sample of 46 classical Cepheids with precise photometric and radial velocity data from Gaia DR3 was analysed. Model fitting was conducted by directly comparing predicted and observed variations in GaiaG , G_BP, and G_RP light curves, as well as radial velocity time series. Distances inferred from the models were compared to Gaia parallaxes, including corrections provided by the Gaia team. Predicted masses and luminosities were used to constrain the ML relation, while the inclusion of radial velocity curves allowed for an independent estimation of the p-factor.

Resuts. The comparison between inferred distances and Gaia parallaxes reveals a statistical agreement, indicating no need foradditional global offset corrections. The predicted masses and luminosities are consistent with an evolutionary scenario that includes a small or mild amount of core overshooting, mass loss, or rotation. Our analysis of the p-factor does not suggest a significant period dependence, with a constant value of p = 1.22 ° 0.05 , which is consistent with recent literature. Additionally, our results align well with the recent period–Wesenheit–metallicity relation derived from Gaia DR3 photometric magnitudes combined with parallax measurements.