A Study of the Pulsation Properties of 57 Non-Blazhko Ab-type RR Lyrae Stars with Homogeneous Metallicities from the LAMOST–Kepler/K2 Survey

Abstract

Homogeneous metallicities and continuous high-precision light curves play key roles in studying the pulsation properties of RR Lyrae stars. By cross matching LAMOST DR6 with the Kepler and K2 fields, we have determined seven and 50 non-Blazhko RRab stars, respectively, that have homogeneous metallicities determined from low-resolution spectra of the LAMOST–Kepler/K2 survey. The Fourier decomposition method is applied to the light curves of these stars provided by the Kepler space-based telescope to determine the fundamental pulsation periods and parameters. The calculated amplitude ratios of R 21, R 31 and the phase differences of ϕ 21, ϕ 31 are consistent with the parameters of RRab stars in both globular clusters and the Large Magellanic Cloud. We find a linear relationship between the phase differences ϕ 21 and ϕ 31, which is in good agreement with the results in the literature. As far as the amplitude, we find that the amplitude of primary frequency A 1 and the total amplitude A tot follow either a cubic or linear relationship. For the rise time, we do not find its relevance with the period of the fundamental pulsation mode P1, or A tot and ϕ 21. However, it might follow a linear relationship with R 31. Based on the homogeneous metallicities, we have derived a new calibration formula for the period–ϕ 31–[Fe/H] relation, which agrees well with previous studies.

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

“…The M21 metallicity is in Crestani et al (2021) scale, therefore we applied an offset of −0.08 dex to convert Fe H Carretta et al (2009) scale as determined in Mullen et al (2021). We did not include V-band relation from Jurcsik & Kovacs (1996) because the qualities for some of the light curves used in their work (as commented in Mullen et al 2021;Zong et al 2023) are not as good as those studied either in M21 or N22.…”

Asteroseismological Analysis of the Non-Blazhko RRab Star EPIC 248846335 in the LAMOST–Kepler/K2 Project

“…The standard deviation of the residuals of the Fourier decomposition that applies to the light curve observed by K2 is σ LC = 0.008 mag. Adopting the methodology of Zong et al (2023), we calculate the total amplitudes A tot and the rise times (RTs) of the light and RV curves, with the fitted parameters listed in Table 1.…”