New near-infrared JHKs light-curve templates for RR Lyrae variables

We provide homogeneous optical (UBVRI) and near-infrared (NIR,JHK) time series photometry for 254 cluster (ωCen, M 4) and field RR Lyrae(RRL) variables. We ended up with more than 551 000 measurements, of which only 9% are literature data. For 94 fundamental (RRab) and 51first overtones (RRc) we provide a complete optical/NIR characterization (mean magnitudes, luminosity amplitudes, epoch of the anchor point).The NIR light curves of these variables were adopted to provide new light-curve templates for both RRc and RRab variables. The templates fortheJand theHbands are newly introduced, together with the use of the pulsation period to discriminate among the different RRab templates. Toovercome subtle uncertainties in the fit of secondary features of the light curves we provide two independent sets of analytical functions (Fourierand periodic Gaussian series). The new templates were validated by using 26ωCen and Bulge RRLs. We find that the difference between themeasured mean magnitude along the light curve and the mean magnitude estimated by using the template on a single randomly extracted phasepoint is better than 0.01 mag (σ=0.04 mag). We also validated the template on variables for which at least three phase points were available, butwithout information on the phase of the anchor point. We find that the accuracy of the mean magnitudes is also∼0.01 mag (σ=0.04 mag). The newtemplates were applied to the Large Magellanic Cloud (LMC) globular cluster Reticulum and by using literature data and predicted PLZ relationswe find true distance moduliμ=18.47±0.10 (rand.)±0.03 (syst.) mag (J) and 18.49±0.09±0.05 mag (K). We also used literature optical andmid-infrared data and we found a meanμof 18.47±0.02±0.06 mag, suggesting that Reticulum is∼1 kpc closer than the LMC.