Towards self-consistent PLZ relations for RR Lyrae Stars

Pulsating variable stars trace different stellar populations and provide constraints on their age and metallicity. RR Lyrae, in particular, can serve as al alternative to Classical Cepheids in the determination of the Hubble constant, exploiting their period-luminosity-metallicity relation (PLZ) to measure distances up to a few Mpc, with the advantage of being old stars (>10 Gyr) present in almost all environments. However, the relations linking absolute magnitude and pulsational properties of RR Lyrae stars need a better calibration and high-resolution spectroscopy to assess metallicity dependence.In this context, over the past years, we have been focused in the reduction and calibration of data from a set of bright RR Lyrae stars with high-precision parallaxes in the Gaia archive. These data were gathered from a number of instruments and observatories (IAC80, Stella, INT, Mercator, NOT and TNG in the Canary Islands, IRSF in South Africa). With this, we have obtained refined periods and high precision magnitudes (in the optical, UBVRI, with 89 stars, and in the near infrared, JHK, with 131 stars) and metallicities of these stars. With the objective of achieving a proper fit for the PLZ relation, we have also analysed the lightcurves of a sample of RR Lyrae hosted by globular clusters with know [Fe/H], both in the optical and NIR. Here, we present the result of the calibration of a homogeneus, multiwavelength PLZ and PWZ, and its application to compute the distance to some structures in our Milky Way.