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.

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

Magurno D.;Dall'Ora M.;Fiorentino G.;Iannicola G.;Marinoni S.;
2019

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.
THE ASTROPHYSICAL JOURNAL
Magurno D.; Sneden C.; Bono G.; Braga V.F.; Mateo M.; Persson S.E.; Preston G.; Thevenin F.; Silva R.D.; Dall'Ora M.; Fabrizio M.; Ferraro I.; Fiorentino G.; Iannicola G.; Inno L.; Marengo M.; Marinoni S.; Marrese P.M.; Martinez-Vazquez C.E.; Matsunaga N.; Monelli M.; Neeley J.R.; Nonino M.; Walker A.R.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/718681
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