2025AJ....170..189S

We utilize a set of internally consistent absolute ages for a sample of ten Galactic globular clusters to determine the variation of the slope with the zero point of the M_V(RR) ∼ [Fe/H] relation for RR Lyrae variables. Our formalism relies on numerical modeling of the main sequence turnoff magnitude in the V band as a function of age, [Fe/H] and [α/Fe] using two different sets of theoretical isochrones. These are then combined with the aforementioned absolute cluster ages and observed values of the magnitude difference between the main-sequence turnoff and the horizontal branch (i.e., ΔV(TO - HB)) for each cluster to calculate relations between the slope and zero point of the M_V(RR) ∼ [Fe/H] relation within this paradigm. Based on this analysis, our preferred relation is of the form M_V(RR) = 0.20[Fe/H] + 0.81 as presented in this work.