Hierarchical Bayesian model to infer PL(Z) relations using Gaia parallaxes H. E. Delgado, L. M. Sarro, G. Clementini, T. Muraveva and A. Garofalo A&A, 623 (2019) A156 Published online: 26 March 2019 DOI: 10.1051/0004-6361/201832945