On the Use of Field RR Lyrae as Galactic Probes. II. A new $\Delta$S calibration to estimate their metallicity

J. Crestani, M. Fabrizio, V. F. Braga +33

We performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). We secured $\approx$6,300 high resolution (HR, R$\sim$35,000) spectra for 143 RRLs (11…