Massive binaries as the source of abundance anomalies in globular clusters

By Selma de Mink, O. Pols, N. Langer, N. Langer, Robert G. Izzard. 2009

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Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch (AGB) stars and massive stars rotating near the break-up limit (spin stars). We propose massive binaries as an alternative source of processed material. We compute the evolution of a 20 M star in a close binary considering the effects of non conservative mass and angular momentum transfer and of rotation and tidal interaction to demonstrate the principle. We find that this system sheds about 10 M of material, nearly the entire envelope of the primary star. The ejecta are enriched in He, N, Na, and Al and depleted in C and O, similar to the abundance patterns observed in gobular cluster stars. However, Mg is not significantly depleted in the ejecta of this model. In contrast to the fast, radiatively driven winds of massive stars, this material is typically ejected with low velocity. We expect that it remains inside the potential well of a globular cluster and becomes available for the formation or pollution of a second generation of stars. We estimate that the amount of processed low-velocity material ejected by massive binaries is greater than the contribution of AGB stars and spin stars combined, assuming that the majority of massive stars in a proto-globular cluster interact with a companion and return their envelope to the interstellar medium. If we take the possible contribution of intermediate mass stars in binaries into account and assume that the ejecta are diluted with an equal amount of unprocessed material, we find that this scenario can potentially provide enough material to form a second generation of low-mass stars, which is as numerous as the first generation of low-mass stars, without the need to make commonly adopted assumptions, such as preferential loss of the first generation of stars, external pollution of the cluster, or an anomalous initial mass function.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fda4d3e1d7ad82929acf617d997c4eb2d67ce598

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Citations in the corpus

Modeling Dense Star Clusters in the Milky Way and Beyond with the CMC Cluster Catalog (2019, background): “In particular, studies of MPs can place important constraints on various cluster processes, especially those occurring during the earliest evolutionary phases of clusters (e.g., Ventura et al. 2001; Decressin et al. 2007; de Mink et al. 2009; Denissenkov & Hartwick 2014; Gieles et al. 2018).”
THE ROTATION RATES OF MASSIVE STARS: THE ROLE OF BINARY INTERACTION THROUGH TIDES, MASS TRANSFER, AND MERGERS (2012, background): “In the models by Petrovic et al. (2005) and de Mink et al. (2009b), it was assumed that accretion ceases when the star reaches the Keplerian limit.”
Multiple populations in globular clusters (2012, background): “However, D’Ercole et al. (2011) and D’Antona et al.”
THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS. I. OVERVIEW OF THE PROJECT AND DETECTION OF MULTIPLE STELLAR POPULATIONS (2014, background): “…branch (AGB-M) stars (DAntona et al. 2002), fast-rotating massive stars (FRMS) (Decressin et al. 2007), or interacting massive binary stars (de Mink et al. 2009, Vanbeveren et al. 2012) may eject materials with composition similar to that of 2G stars, i.e., somewhat helium enriched and…”
The Hubble Space TelescopeUV Legacy Survey of Galactic Globular Clusters – V. Constraints on formation scenarios (2015, background): “…order of decreasing mass: i) supermassive stars (SMS,∼ 104 M⊙, Denissenkov & Hartwick 2014), ii) massive interacting binar es (MIB, e.g., 15+ 20M⊙, de Mink et al. 2009; Bastian et al. 2013), iii) fast-rotating massive stars (FRMS,∼ 25−120M⊙, Krause et al. 2013) and iv) asymptotic giant branch…”
Globular clusters as the relics of regular star formation in ‘normal’ high-redshift galaxies (2015, background): “…of asecond generation of stars from retained FRMS ejecta (< 10 Myr after the formation of the first generation). c© 2015 RAS, MNRAS000, 1–29 (iii) Enrichment by the early disc accretion (EDA) of winds from FRMSs and massive interacting binaries (MIBs;de Mink et al. 2009; Bastian et al. 2013b).”
The second and third parameters of the horizontal branch in globular clusters (2010, background): “…O and Mg, we do not yet have a satisfactory detailed model, and even its astrophysical basis is currently debated (either fast rotating massive stars or massive AGB stars, experiencing hot bottom burning, or massive binaries: see Decressin et al. 2007; Ventura et al. 2001; De Mink et al. 2009).”
The two metallicity groups of the globular cluster M 22: a chemical perspective (2011, background): “Candidate first-generation element donors include intermediate mass asymptotic giant branch (AGB) stars (D’Antona & Caloi 2004), fast rotating massive stars (Decressin et al. 2007), and/or massive binaries (de Mink et al. 2009).”
THE INCIDENCE OF STELLAR MERGERS AND MASS GAINERS AMONG MASSIVE STARS (2013, result): “This latter case is indicated as β = βK and is equal to the assumptions made in Petrovic et al. (2005) and de Mink et al. (2009).”
MULTIPLE STELLAR POPULATIONS IN 47 Tucanae (2011, background): “…Galactic GCs (see Gratton et al. 2004 for a review), possibly in combination with accretion onto low-mass stars of ejecta from either intermediate-mass stars (D’Antona et al. 1983; Renzini 1983), fast-rotating massive stars (e.g., Decressin et al. 2007), or massive binaries (De Mink et al. 2009).”