Evaluating the V-band Photometric Metallicity with Fundamental Mode RR Lyrae in the Kepler Field

TL;DR

This study assesses the accuracy of photometric metallicity estimates for RR Lyrae stars in the Kepler field, demonstrating that including a color-term improves agreement with spectroscopic measurements and deriving new metallicity relations.

Contribution

The paper introduces a method to accurately determine photometric metallicity from V-band light-curves transformed from gr-band data, emphasizing the importance of a color-term and validating the approach with Kepler RR Lyrae stars.

Findings

Including a color-term improves photometric [Fe/H] accuracy.

Blazhko RR Lyrae can still provide consistent metallicity estimates.

Derived new gVr-band [Fe/H]-${phi}_{31}$-P relations that align with recent literature.

Abstract

The aim of this work is to evaluate the performance of photometric metallicity [Fe/H], determined based on V-band light-curves photometrically transformed from the gr-band light-curves. We tested this by using a set of homogeneous sample of fundamental mode RR Lyrae located in the Kepler field. It was found that the color-term is necessary in such photometric transformation. We demonstrated that including the color-term the determined photometric [Fe/H] are in good agreement to the spectroscopic [Fe/H], either based on the calibrated or the transformed V-band light-curves. We also tested the impact of Blazhko RR Lyrae in determining the photometric Fe/H], and found that Blazhko RR Lyrae can give consistent photometric [Fe/H]. Finally, we derived independent gVr-band [Fe/H]-$\phi_{31}$-P relations (where $\phi_{31}$ and P are Fourier parameter and pulsation period, respectively) using our light-curves. The V-band relation is in good agreement with the most recent determination given in the literature.