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.

arXiv comment9 pages, 4 figures, accepted for publication by ApJL

References in corpus (24)

• Omega Centauri: The Population Puzzle Goes Deeper
• Detecting Bimodality in Astronomical Datasets
• Metallicities on the Double Main Sequence of omega Centauri Imply Large Helium Enhancement
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• A helium spread among the main sequence stars in NGC 2808
• The early evolution of Globular Clusters: the case of NGC 2808
• New evidence for the complex struscture of the RGB of Omega Cen
• A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
• Super Helium-Rich Population and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
• The calibration of the RGB Tip as a Standard Candle: Extension to Near Infrared colors and higher metallicity
• The Abundance Spread Among Giants and Subgiants in the Globular Cluster Omega Centauri
• Metallicities, relative ages and kinematics of stellar populations in omega Centauri
• Towards the absolute planes: a new calibration of the Bolometric Corrections and Temperature scales for Population II Giants
• High resolution spectroscopy of metal rich giants in omega Cen: first indication of SNe Ia enrichment
• RR Lyrae stars in Galactic globular clusters. II. A theoretical approach to variables in M3
• Discovery of an anomalous Sub Giant Branch in the Color Magnitude Diagram of omega Centauri
• CCD Photometry of the Globular Cluster omega Centauri. II. Stellar Populations and Age-Metallicity Relation
• The extended star formation history of omega Centauri
• CCD Photometry of the Globular Cluster Omega Centauri. I. Metallicity of RR Lyrae Stars from Caby Photometry
• Cluster AgeS Experiment. Catalog of Variable Stars in the Globular Cluster Omega Centauri
• A Catalog of Helium Abundance Indicators from Globular Cluster Photometry
• The Most Exciting Massive Binary Cluster in NGC 5128: Clues to the Formation of Globular Clusters
• IR photometric properties of Red Giants in omega Cen
• Discovery of a Variable Star Population in NGC 2808

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• On a new theoretical framework for RR Lyrae stars I: the metallicity dependence
• The multiplicity of the subgiant branch of Omega Centauri: Evidence for prolonged star formation
• 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/H] relations for c-type RR Lyrae Variables based upon Fourier Coefficients
• Star Formation Histories of Globular Clusters with Multiple Populations. I. ω Cen, M22, and NGC 1851
• A pulsational distance to Omega Centauri based on Near-Infrared Period-Luminosity relations of RR Lyrae stars
• 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
• The mosaic multiple stellar populations in $\omega$ Centauri : the Horizontal Branch and the Main Sequence
• Star Counts in the Globular Cluster Omega Centauri. I. Bright Stellar Components
• 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
• RR Lyrae Atmospherics: Wrinkles Old and New. A Preview
• High-precision distance measurements with classical pulsating stars
• Metallicity Analysis of MACHO Galactic Bulge RR0 Lyrae stars from their Lightcurves
• On the RR Lyrae stars in globulars: V. the complete Near-Infrared (JHKs) census of omega Centauri RR Lyrae variables
• Variable stars in the Globular Cluster NGC 2808
• On the Impact of Helium Content on the RR Lyrae Distance Scale
• RR Lyrae variables in Messier 53: Near-infrared Period--Luminosity relations and the calibration using Gaia Early Data Release 3
• A Data-driven Study of RR Lyrae Near-IR Light Curves: Principal Component Analysis, Robust Fits, and Metallicity Estimates
• On a new method to estimate distance, reddening and metallicity of RR Lyrae stars using optical/near-infrared ($B$,$V$,$I$,$J$,$H$,$K$) mean magnitudes: $\omega$ Centauri as a first test case
• 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
• On the period distribution of cluster RR Lyrae stars to constrain their helium content: the case of omega Centauri
• Complex stellar populations in massive clusters: trapping stars of a dwarf-disc galaxy in a newborn stellar super-cluster
• Chemical Compositions of Field and Globular Cluster RR~Lyrae Stars: II. omega Centauri
• An Updated Census of RR~Lyrae Stars in the Globular Cluster $\omega$~Centauri (NGC\,5139)
• Period Change Similarities among the RR Lyrae Variables in Oosterhoff I and Oosterhoff II Globular Systems
• On the origin of the helium-rich population in Omega Centauri
• Infrared $K_s$-band Photometry of Field RR Lyrae Variable Stars
• Near-IR period-luminosity relations for pulsating stars in $\omega$ 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
• Revisiting Delta Y/Delta Z from multiple main sequences in Globular Clusters: insight from nearby stars
• Identifying Contaminated K-band Globular Cluster RR Lyrae Photometry
• Predicting light curves of RR Lyrae variables using artificial neural network based interpolation of a grid of pulsation models
• SMHASH: A new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor
• Globular clusters as laboratories for stellar evolution
• On the origin of the helium-rich population in the peculiar globular cluster Omega Centauri