A vindication of the RR Lyrae Fourier light curve decomposition for the calculation of metallicity and distance in globular clusters
arXiv:2204.01953 · doi:10.22201/ia.01851101p.2022.58.02.08
Abstract
We report the mean metallicity and absolute magnitude of RR Lyrae stars in a sample of 37 globular clusters, calculated via the Fourier decomposition of their light curves and ad hoc semiempirical calibrations, in an unprecedented homogeneous approach. This enabled a new discussion of the metallicity dependence of the horizontal branch (HB) luminosity, as a fundamental distance indicator. The calibration for the RRab and RRc stars should be treated separately. For the RRab the dispersion is larger and non-linear. For the RRc stars the correlation is less steep, very tight and linear. The relevance of the HB structural parameter L, is highlighted and offer a non-linear calibration of the form MV ([Fe/H],L). Excellent agreement is found between values of [Fe/H] and MV from the light curve decomposition with spectroscopic values and distances obtained via Gaia-DR3 and HST. The variable stars census in 35 clusters includes 326 stars found by our program.
arXiv comment17 pages, 4 figures, 3 tables. arXiv admin note: text overlap with arXiv:1701.02719
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