A New RR Lyrae Metallicity Calibration

Abstract

We have begun developing a new metallicity calibration for RR Lyrae stars that includes high-temperature phase regions. Our calibration is an updated and expanded version of the Delta-S, equivalent width method, but which is applicable for most phases of the pulsation, and for the hotter, shorter-period RRc stars. This calibration will be constructed from spectral observations of well studied, bright RR Lyrae stars with metallicities from published high-resolution studies, within the range $-2.5 < [Fe/H] < -0.3$. Phase information for our calibration stars were taken from the AAVSO website, and the MacAdam Student Observatory at the University of Kentucky. Low-resolution spectroscopy $(R \sim 1000)$ was obtained using the McDonald Observatory, 2.1 meter telescope. Here we present our preliminary data, and find the phase region where the calibration will break down.