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

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.Comment: 12 pages, 2 Tables and 7 Figures; AJ accepte

Photometric Metallicity and Distance for the Two RR Lyrae in Segue II and Ursa Major II Dwarf Galaxies Based on Multi-Band Light-Curves

Multi-band light curves of two RR Lyrae variables in Segue II and Ursa Major II ultra-faint dwarf (UFD) galaxies were collected from near simultaneous observations using the Lulin One-meter Telescope in Vgri bands. Together with Gaia G-band light curves, we determined photometric metallicities using empirical relations involving pulsation period and Fourier parameter as dependent parameters. We demonstrated that the RR Lyrae photometric metallicity can be determined accurately when these empirical relations were employed at multiple wavelengths, which can potentially improve the distance determination based on RR Lyrae stars. The photometric metallicities based on our approach were found to be $-2.27\pm0.13$ dex and $-1.87\pm0.16$ dex for the RR Lyrae in Segue II and Ursa Major II UFD, respectively, with corresponding distance moduli of $17.69\pm0.15$ mag and $17.58\pm0.15$ mag, in agreement with previous literature determinations. This approach of photometric metallicity of RR Lyrae based on multi-band optical light curves will be particularly relevant for distance measurements in the era of the Vera C Rubin's Legacy Survey of Space and Time.Comment: 9 pages, 3 figures and 5 tables, AJ accepte

Preliminary Analysis of ULPC Light Curves Using Fourier Decomposition Technique

Recent work on Ultra Long Period Cepheids (ULPCs) has suggested their usefulness as a distance indicator, but has not commented on their relationship as compared with other types of variable stars. In this work, we use Fourier analysis to quantify the structure of ULPC light curves and compare them to Classical Cepheids and Mira variables. Our preliminary results suggest that the low order Fourier parameters of ULPCs show a continuous trend defined by Classical Cepheids after the resonance around 10 days. However their Fourier parameters also overlapped with those from Miras, which make the classification of long period variable stars difficult based on the light curves information alone.Comment: 6 pages, 3 tables and 4 figures. Published in IEEE Xplore for 2013 IEEE International Conference on Space Science and Communication (IconSpace2013