Alterations of the [Fe/H] Values Modulate Light Curves by Absolute Magnitude in non-Blazhko RRab Lyraes

RR Lyraes are a type of variable star known for their short periods and their periodicity can be used as standard candles to determine the distances of interstellar objects they reside in. The correlation between the composition of RR Lyraes and their light curves is not well understood. This study investigated the relationship between the metallicity and resulting changes in the light curves of non-Blazhko RRab Lyraes. We analyzed 135 images of the 15 RR Lyraes throughout nine periods of the day by remotely accessing the Canary 2 telescope at the Slooh Canary Islands Observatory. We examined the images using multiple image analysis software programs to find locator stars, determine the apparent magnitudes of the RR Lyraes, and create light curves. We observed a negative exponential relationship between the [Fe/H] and the light curve amplitudes of the RR Lyraes, and a negative linear relationship between the [Fe/H] and the periods of the RR Lyraes. These results demonstrate that we can obtain a better idea of an RR Lyrae’s composition based on solely its light curve and that characteristics of a light curve can be predicted based off of metallicity without time-consuming visual observations being required. These conclusions will assist in applying metallicity corrections to obtain more precise absolute magnitudes of the RR Lyraes so that they may be more effective standard candles.