New Metallicities of RR Lyrae Stars in omega Centauri: Evidence for a Non He-Enhanced Metal-Intermediate Population

Abstract

We present new spectroscopic metal abundances for 74 RR Lyrae stars in omega Cen obtained with FLAMES. The well-known metallicity spread is visible among the RR Lyrae variables. The metal-intermediate (MInt) RR Lyrae stars ([Fe/H] ~ -1.2) are fainter than the bulk of the dominant metal-poor population ([Fe/H] ~ -1.7), in good agreement with the corresponding zero-age horizontal branch models with cosmological helium abundance Y = 0.246. This result conflicts with the hypothesis that the progenitors of the MInt RR Lyrae stars correspond to the anomalous blue main-sequence stars, which share a similar metallicity but whose properties are currently explained by assuming for them a large helium enhancement. Therefore, in this scenario, the coexistence within the cluster of two different populations with similar metallicities ([Fe/H] ~ -1.2) and different helium abundances has to be considered.

9 pages, 4 figures, accepted for publication by ApJL

Cited by in corpus (21)

• Deep FORS1 observations of the double Main Sequence of omega Centauri
• The RR Lyrae Period - K Luminosity relation for Globular Clusters: an observational approach
• The period-luminosity relation for type II Cepheids in globular clusters
• Origin of Abundance Inhomogeneity in Globular Clusters
• Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• On the RR Lyrae stars in globulars: IV. $\omega$ Centauri Optical UBVRI Photometry
• RR Lyrae stars in Galactic globular clusters. VI. The Period-Amplitude relation
• A spectral atlas of post-main-sequence stars in omega Centauri: kinematics, evolution, enrichment and interstellar medium
• The chemical evolution of Omega Centauri's progenitor system
• High-precision distance measurements with classical pulsating stars
• Metallicity Analysis of MACHO Galactic Bulge RR0 Lyrae stars from their Lightcurves
• RR Lyrae variables in Messier 53: Near-infrared Period--Luminosity relations and the calibration using Gaia Early Data Release 3
• Computation of the Fourier parameters of RR Lyrae stars by template fitting
• Searching for tidal tails around $\omega$ Centauri using RR Lyrae Stars
• New Near-Infrared $JH{K}_s$ light-curve templates for RR Lyrae variables
• Complex stellar populations in massive clusters: trapping stars of a dwarf-disc galaxy in a newborn stellar super-cluster
• An Updated Census of RR~Lyrae Stars in the Globular Cluster $\omega$~Centauri (NGC\,5139)
• Observational consequences of the hypothesized helium rich stellar population in Omega Centauri
• Testing the AGB Scenario as the Origin of the Extreme-Helium Population in omega Centauri
• Surface pollution of main-sequence stars through encounters with AGB ejecta in omega Centauri
• Predicting light curves of RR Lyrae variables using artificial neural network based interpolation of a grid of pulsation models