Chemical Compositions of Field and Globular Cluster RR Lyrae Stars. II. ω Centauri

D. Magurno, C. Sneden, G. Bono, V. F. Braga, M. Mateo, S. E. Persson, G. Preston, F. Thévenin, R. Da Silva, M. Dall'Ora, M. Fabrizio, I. Ferraro, G. Fiorentino, G. Iannicola, L. Inno, M. Marengo, S. Marinoni, P. M. Marrese, C. E. Martínez-Vázquez, N. MatsunagaM. Monelli, J. R. Neeley, M. Nonino, A. R. Walker

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

We present a detailed spectroscopic analysis of RR Lyrae (RRL) variables in the globular cluster NGC 5139 (ω Cen). We collected optical (4580-5330 Å), high-resolution (R ∼ 34,000), high signal-to-noise ratio (∼200) spectra for 113 RRLs with the multifiber spectrograph M2FS at the Magellan/Clay Telescope at Las Campanas Observatory. We also analyzed high-resolution (R ∼ 26,000) spectra for 122 RRLs collected with FLAMES/GIRAFFE at the Very Large Telescope, available in the ESO archive. The current sample doubles the literature abundances of cluster and field RRLs in the Milky Way based on high-resolution spectra. Equivalent-width measurements were used to estimate atmospheric parameters, iron, and abundance ratios for α (Mg, Ca, Ti), iron peak (Sc, Cr, Ni, Zn), and s-process (Y) elements. We confirm that ω Cen is a complex cluster, characterized by a large spread in the iron content: -2.58 ≤ [Fe/H] ≤ -0.85. We estimated the average cluster abundance as , with σ = 0.33 dex. Our findings also suggest that two different RRL populations coexist in the cluster. The former is more metal-poor ([Fe/H] ≲ - 1.5), with almost solar abundance of Y. The latter is less numerous, more metal-rich, and yttrium enhanced ([Y/Fe] ⪆ 0.4). This peculiar bimodal enrichment only shows up in the s-process element, and it is not observed among lighter elements, whose [X/Fe] ratios are typical for Galactic globular clusters.

Original languageEnglish
Article number104
JournalAstrophysical Journal
Volume881
Issue number2
DOIs
Publication statusPublished - 20 Aug 2019

Keywords

  • globular clusters: individual (NGC 5139)
  • stars: abundances
  • stars: variables: RR Lyrae
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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