Metallicity of Gal. RR Lyrae from opt. & IR LCs

This work's calibration data set provides the largest and most comprehensive span of parameter space to date, with homogeneous metallicities from -3<~[Fe/H]<~0.4 and accurate Fourier parameters derived from 1980 ASAS-SN (V band) and 1083 WISE (NEOWISE extension, W1 and W2 bands) RR Lyrae stars with well-sampled light curves.

We compare our optical period-{phi}_31_-[Fe/H] relation with those available in the literature and demonstrate that our relation minimizes systematic trends in the lower and higher metallicity range. Moreover, a direct comparison shows that our optical photometric metallicities are consistent with both those from high-resolution spectroscopy and globular clusters, supporting the good performance of our relation. We found an intrinsic scatter in the photometric metallicities (0.41dex in the V band and 0.50dex in the infrared) by utilizing large calibration data sets covering a broad metallicity range.