Gaia parallaxes versus updated model predictions

The Hubble constant tension between the value derived by Riess et al. (2016,2018)

on the basis of Classical Cepheids distances and the Cosmic Microwave Background

results is one of the most debated issues in current astrophysical literature. On the

basis of an updated and extended set of nonlinear convective pulsation models, we

are theoretically investigating the systematic effects on the Cepheid based

extragalactic distance scale and the resulting Hubble constant. The predicted light

curves and pulsation relations for both Galactic and Magellanic Cepheids, based on

these new model sets, are tested on Gaia Data Release 2 (DR2) results.

We find evidence of a Gaia DR2 parallax offset, consistent with independent results

in the literature, but a general good agreement with the distances predicted by our

theoretical pulsation scenario. We discuss the implications of our results and future

perspectives, while waiting for Gaia Data Release 3.