The Helium Abundances of ω Centauri

By J. Norris. 2004

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In Astronomy and Astrophysics

Citations in the corpus

Formation and dynamical evolution of multiple stellar generations in globular clusters (2008, background): “…two clusters, ω Cen and NGC 2808, in which the MS morphology shows that a non negligible fraction of the stars (∼25% in ω Cen , ∼15% in NGC 2808) populate a “blue MS” which can only be interpreted as a very heliumrich MS (Bedin et al. 2004; Norris 2004; Piotto et al. 2005; D’Antona et al. 2005b).”
Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters (2007, background): “It should be noted that some observational features in globular clusters such as the multiple sequences in ω Cen (Bedin et al. 2004) and NGC 2808 (Piotto et al. 2007) are explained by an He enrichment of the low-mass stars up to He 0.4 (Norris 2004; Piotto et al. 2005; D’Antona et al. 2005).”
The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851 (2007, background): “Cen, the multiple populations manifest themselves both in a main-sequence (MS) split (interpreted as a bimodal He abundance; see Bedin et al. 2004; Norris 2004; Piotto et al. 2005) and in a multiplicity of SGBs (interpreted in terms of large age variations, 31 Gyr; see Villanova et al. 2007 and…”
The fraction of second generation stars in globular clusters from the analysis of the horizontal branch (2008, background): “…in the literature, that the ejecta of a unique first stellar generation with a normal initial mass function (IMF) can not produce enough mass to give origin to such a large fraction of second generation stars (see, e.g., the case made by Bekki and Norris (2004), for the blue main sequence of ωCen).”
A WFC3/HST VIEW OF THE THREE STELLAR POPULATIONS IN THE GLOBULAR CLUSTER NGC 6752 (2013, background): “…47 Tuc, NGC6752, and NGC6397 (Anderson 1997, Bedin et al. 2004, Piotto et al. 2007, Milone et al. 2010, 2012a,b), which have been associated with stellar populations with different helium abundances (D’Antona & Caloi 2004, Norris 2004, Bedin et al. 2004, Piotto et al. 2005, D’Antona et al. 2005).”
Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology (2015, background): “However, there is broad agreement on the expected range for the relation being between 1 6 ∆Y/∆Z 6 3 (except for some very pecu- c© 0000 RAS, MNRAS 000, 000–000 liar objects such as ω Centauri, see Norris 2004).”
On the self-enrichment scenario of galactic globular clusters: constraints on the IMF (2006, background): “The idea that WMS may be at the origin of some anomalies in the composition of GCs has been recently suggested by Norris (2004) and Maeder and Meynet (2006), in order to explain the blue main sequence of the cluster ω Centauri: the high helium content of the stars of that sequence could originate…”
The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars (2014, background): “This huge increase in He is one of the reasons why intermediate-mass AGB stars have been implicated in the origin of the multiple populations observed in Galactic GCs (D’Antona et al. 2002; Norris 2004; Piotto et al. 2005).”
Massive AGB models of low metallicity: the implications for the self-enrichment scenario in metal-poor globular clusters (2009, background): “The presence of a fraction of stars enriched in helium has been inferred also by the presence of a blue main sequence in ωCen (Bedin et al. 2004; Norris 2004; Piotto et al. 2005), and in NGC 2808 (Piotto et al. 2007).”
Metallicities on the Double Main Sequence of ω Centauri Imply Large Helium Enhancement (2004, background): “The first one, already raised by Norris (2004), is that in order to elevate Y from 0.24 to ∼0.38 one has to assume that most, if not all the material from which the bMS stars formed is made up of the ejecta of the first generation of stars.”
Super-Helium-rich Populations and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters (2005, background): “More recent analysis, based on the old Revised Yale isochrones (Green et al. 1987), has suggested that a large range of primordial helium abundance variation is needed to reproduce the double MS observed in ω Cen (Norris 2004).”
A Helium Spread among the Main-Sequence Stars in NGC 2808 (2005, background): “In ω Cen, the presence of a high helium MS has been suggested (Bedin et al. 2004; Norris 2004) as one of the possible components needed to explain the complexity of this cluster, where multiple turnoffs and red giant branches have been detected (see, Lee et al. 1999; Pancino et al. 2000; Ferraro et…”
The Adequacy of Stellar Evolution Models for the Interpretation of the Color-Magnitude Diagrams of Resolved Stellar Populations (2005, background): “The uncertainties are related to the fact that the Y-to-Z enrichment ratio ( Y/ Z ) is not well known and probably not unique (e.g., Norris 2004).”
CHEMICAL ABUNDANCES FOR 855 GIANTS IN THE GLOBULAR CLUSTER OMEGA CENTAURI (NGC 5139) (2010, background): “The discovery and subsequent detailed analyses of ω Cen’s blue main sequence (An- derson 1997, 2002; Bedin et al. 2004; Norris 2004; Piotto et al. 2005; Sollima et al. 2007; Bellini et al. 2009b) have revealed that this population represents ∼30% of all main sequence stars, is preferentially…”
The Origin of the Double Main Sequence in ω Centauri: Helium Enrichment due to Gas Fueling from Its Ancient Host Galaxy? (2005, unknown): “A number of recent investigations have suggested that the above scenario (3) (hereafter referred to as the “helium pollution scenario” and abbreviated to “HEPS” for convenience) is the most promising among the four (e.g., Lee et al. 2005; Norris 2004; Piotto et al. 2005).”
Accreted versus in situ Milky Way globular clusters (2010, background): “EHBs in GCs appear to be due to the presence of a heliumenhanced population of stars and hence are a strong indicator for the presence of multiple stellar populations (Norris 2004; Piotto et al. 2005).”
The Multiplicity of the Subgiant Branch of ω Centauri: Evidence for Prolonged Star Formation (2007, methodology): “Following Norris (2004) and B04, we share the view that the bMS component is enriched in helium.”
Origin of multiple stellar populations in globular clusters and their helium enrichment (2008, background): “Then came the discovery that also its main sequence (MS) splits into two parallel sequences, with the bluer one being more metal rich by nearly a factor of 2, hence indicating a higher helium abundance (Bedin et al. 2004; Norris 2004; Piotto et al. 2005).”