Analysis shows slope variation of MV (RR) ∼ [Fe/H] for RR Lyrae in galactic clusters, suggesting implications for stellar evolution.
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., Δ V (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.
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Ata Sarajedini (2025) studied this question.
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