New metallicities of RR Lyrae stars in omega Centauri: Evidence for a non-He-enhanced metal-intermediate population

Sollima, A; Borissova, J.; Catelan, M.; SMITH, HA; Minniti, D; Cacciari, C.; Ferraro, FR

Abstract

We present new spectroscopic metal abundances for 74 RR Lyrae (RRL) stars in ω Cen obtained with FLAMES. The well-known metallicity spread is visible among the RRL variables. The metal-intermediate (MI) RRL 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 MI RRL 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. © 2006. The American Astronomical Society. All rights reserved.

Más información

Título según WOS: New metallicities of RR Lyrae stars in omega Centauri: Evidence for a non-He-enhanced metal-intermediate population
Título según SCOPUS: New metallicities of RR Lyrae stars in ? centauri: Evidence for a non-He-enhanced metal-intermediate population
Título de la Revista: ASTROPHYSICAL JOURNAL
Volumen: 640
Número: 1
Editorial: IOP PUBLISHING LTD
Fecha de publicación: 2006
Página de inicio: L43
Página final: L46
Idioma: English
URL: http://stacks.iop.org/1538-4357/640/i=1/a=L43
DOI:

10.1086/503099

Notas: ISI, SCOPUS