Metallicity Estimation of RR Lyrae Stars From Their I-Band Light Curves

We have revisited the problem of metallicity prediction RR Lyrae stars from their near-infrared light curves in Cousins I waveband. Our study is based on high-quality time-series photometry and state-of-the-art high-resolution spectroscopic abundance measurements 80 fundamental-mode (RRab) 24 first-overtone (RRc) stars, spanning $\sim$[$-2.7$,$+0.18$] dex $\sim$[$-3$,$-0.5$] ranges, respectively. Employing machine-learning methods, we investigated various light-curve representations regression models to identify optimal form for our objective. Accurate new empirical relations between [Fe/H] iron parameters been obtained using Bayesian both RRab RRc with mean absolute errors 0.16 0.18 dex, found that earlier $I$-band estimates had a systematic positive bias up $\sim 0.4$ metal-poor regime. predictive were deployed large ensembles obtain photometric distribution functions (MDFs) old stellar populations around Milky Way. find mode bulge component's MDF approximately $-1.4$ remarkable agreement latest result. Furthermore, derive modes $-1.83$, $-2.13$, $-1.77$ Large Small Magellanic Clouds, Sagittarius dwarf galaxy,