Theoretical fits of the \delta Cephei light, radius and radial velocity curves

TL;DR

This paper presents a theoretical model fitting the light, radius, and radial velocity curves of δ Cephei, achieving high accuracy and providing insights into its chemical composition and distance measurements.

Contribution

It offers a detailed theoretical fit of δ Cephei's observational data, improving understanding of its physical properties and distance estimations.

Findings

Model fits luminosity and velocity amplitudes within 0.8σ.

Radius amplitude fit within 1.7σ.

Distance estimates from light curves align with HST parallax within 0.8σ.

Abstract

We present a theoretical investigation of the light, radius and radial velocity variations of the prototype $\delta$ Cephei. We find that the best fit model accounts for luminosity and velocity amplitudes with an accuracy better than $0.8\sigma$, and for the radius amplitude with an accuracy of $1.7\sigma$. The chemical composition of this model suggests a decrease in both helium (0.26 vs 0.28) and metal (0.01 vs 0.02) content in the solar neighborhood. Moreover, distance determinations based on the fit of light curves agree at the $0.8\sigma$ level with the trigonometric parallax measured by the Hubble Space Telescope (HST). On the other hand, distance determinations based on angular diameter variations, that are independent of interstellar extinction and of the $p$-factor value, indicate an increase of the order of 5% in the HST parallax.