We present new nonlinear , time-dependent convective hydrodynamical models of RR Lyrae stars computed assuming a constant helium-to-metal enrichment ratio and a broad range in metal abundances ( Z = 0.0001 – 0.02 ) .
The stellar masses and luminosities adopted to construct the pulsation models were fixed according to detailed central He burning Horizontal Branch evolutionary models .
The pulsation models cover a broad range in stellar luminosity and effective temperatures and the modal stability is investigated for both fundamental and first overtones .
We predict the topology of the instability strip as a function of the metal content and new analytical relations for the edges of the instability strip in the observational plane .
Moreover , a new analytical relation to constrain the pulsation mass of double pulsators as a function of the period ratio and the metal content is provided .
We derive new Period-Radius-Metallicity relations for fundamental and first-overtone pulsators .
They agree quite well with similar empirical and theoretical relations in the literature .
From the predicted bolometric light curves , transformed into optical ( UBVRI ) and near-infrared ( JHK ) bands , we compute the intensity-averaged mean magnitudes along the entire pulsation cycle and , in turn , new and homogenous metal-dependent ( RIJHK ) Period-Luminosity relations .
Moreover , we compute new dual and triple band optical , optical–NIR and NIR Period-Wesenheit-Metallicity relations .
Interestingly , we find that the optical Period-W ( V,B - V ) is independent of the metal content and that the accuracy of individual distances is a balance between the adopted diagnostics and the precision of photometric and spectroscopic datasets .