Accretion of sub-stellar companions as the origin of chemical abundance inhomogeneities in globular clusters

Abstract

Globular clusters exhibit abundance variations, defining `multiple populations', which have prompted a protracted search for their origin. Properties requiring explanation include: the high fraction of polluted stars ($\sim 40-90$~percent, correlated with cluster mass), the absence of pollution in young clusters and the lower pollution rate with binarity and distance from the cluster centre. We present a novel mechanism for late delivery of pollutants into stars via accretion of sub-stellar companions. In this scenario, stars move through a medium polluted with AGB and massive star ejecta, accreting material to produce companions with typical mass ratio $q\sim 0.1$. These companions undergo eccentricity excitation due to dynamical perturbations by passing stars, culminating in a merger with their host star. The accretion of the companion alters surface abundances via injected pollutant. Alongside other self-enrichment models, the companion accretion model can explain the dilution of pollutant and correlation with intra-cluster location. The model also explains the ubiquity and discreteness of the populations and correlations of enrichment rates with cluster mass, cluster age and stellar binarity. Abundance variations in some clusters can be broadly reproduced using AGB and massive binary ejecta abundances from the literature. In other clusters, some high companion mass ratios ($q\gtrsim 1$) are required. In these cases, the available mass budget necessitates a variable degree of mixing of the polluted material with the primary star, deviations from model ejecta abundances or mixing of internal burning products. We highlight the avenues of further investigation which are required to explore some of the key processes invoked in this model.

29 pages, 20 figures, accepted for publication in MNRAS

References in corpus (59)

• Binary interaction dominates the evolution of massive stars
• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• Stellar Models and Yields of Asymptotic Giant Branch Stars
• Photoevaporation of protoplanetary discs I: hydrodynamic models
• On the self-enrichment scenario of galactic globular clusters: Constraints on the IMF
• Before the first supernova: combined effects of HII regions and winds on molecular clouds
• The Extreme Ultraviolet and X-Ray Sun in Time: High-Energy Evolutionary Tracks of a Solar-Like Star
• Age Determination of Six Intermediate-age SMC Star Clusters with HST/ACS
• Star Formation Around Super-Massive Black Holes
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• A General Abundance Problem for All Self-Enrichment Scenarios for the Origin of Multiple Populations in Globular Clusters
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIX. A Chemical Tagging of the Multiple Stellar Populations Over the Chromosome Maps
• Super and massive AGB stars - III. Nucleosynthesis in metal-poor and very metal-poor stars - Z=0.001 and 0.0001
• Simulations of the formation of stellar discs in the Galactic centre via cloud-cloud collisions
• On the Origin of the High Helium Sequence in $\omega$ Centauri
• Multiple stellar populations in Magellanic Cloud clusters. III. The first evidence of an extended main sequence turn-off in a young cluster: NGC1856
• Rotating Stellar Models Can Account for the Extended Main Sequence Turnoffs in Intermediate Age Clusters
• Cloudlet capture by Transitional Disk and FU Orionis stars
• The possible role of stellar mergers for the formation of multiple stellar populations in globular clusters
• Optically thick HI dominant in the local interstellar medium; an alternative interpretation to "dark gas"
• Sodium and Oxygen Abundances in the Open Cluster NGC 6791 from APOGEE H-Band Spectroscopy
• Effects of close binary evolution on the main-sequence morphology of young star clusters
• First evidence of fully spatially mixed first and second generations in globular clusters: the case of NGC 6362
• `Tail-end' Bondi-Hoyle accretion in young star clusters: Implications for disks, planets, and stars
• Constraining globular cluster formation through studies of young massive clusters - V. ALMA observations of clusters in the Antennae
• Accretion of pristine gas and dilution during the formation of multiple-population globular clusters
• The search for multiple populations in Magellanic Clouds clusters - V. Correlation between cluster age and abundance spreads
• Revisiting nucleosynthesis in globular clusters: the case of NGC 2808 and the role of He and K
• Radial distributions of sub-populations in the globular cluster M15: a more centrally concentrated primordial population
• Constraining globular cluster formation through studies of young massive clusters - III. A lack of gas and dust in massive stellar clusters in the LMC and SMC
• Evolution of stellar collision products in open clusters. II. A grid of low-mass collisions
• The globular cluster NGC 1978 in the Large Magellanic Cloud
• Lithium abundances in globular cluster giants: NGC 1904, NGC 2808, and NGC 362
• Binarity as the Origin of Long Secondary Periods in Red Giant Stars
• The formation of secondary stellar generations in massive young star clusters from rapidly cooling shocked stellar winds
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. X. The radial distribution of stellar populations in NGC 2808
• Protoplanetary Disc Response to Distant Tidal Encounters in Stellar Clusters
• Hot Jupiters driven by high-eccentricity migration in globular clusters
• Dynamical masses and mass-to-light ratios of resolved massive star clusters -- II. Results for 26 star clusters in the Magellanic Clouds
• The influence of the environment on the spin evolution of low-mass stars. I. External photoevaporation of circumstellar disks
• On the accuracy of HI observations in molecular clouds -- More cold HI than thought?
• Expanding the time domain of multiple populations: evidences of nitrogen variations in the ~1.5 Gyr old star cluster NGC 1783
• Heart of Darkness: dust obscuration of the central stellar component in globular clusters younger than ~100Myr in multiple stellar population models
• On the determination of the He abundance distribution in globular clusters from the width of the main sequence
• Leveraging HST with MUSE: I. Sodium abundance variations within the 2 Gyr-old cluster NGC 1978
• Photometric characterization of multiple populations in star clusters: The impact of the first dredge-up
• The loss of the intra-cluster medium in globular clusters
• NGC1818 unveils the origin of the extended main-sequence turn-off in young Magellanic Clouds clusters
• Ionising Feedback Effects on Star Formation in Globular Clusters with Multiple Stellar Populations
• Globular Cluster Intrinsic Iron Abundance Spreads: II. Protocluster Metallicities and the Age-Metallicity Relations of Milky Way Progenitors
• Forming short period sub-stellar companions in 47 Tucanae -- II. Analytic expressions for the orbital evolution of planets in dense environments
• Rethinking Globular Cluster Formation
• Forming short period sub-stellar companions in 47 Tuc: I. Dynamical model and brown dwarf tidal capture rates

Cited by in corpus (3)

• Spatially correlated stellar accretion in the Lupus star forming region: Evidence for ongoing infall from the interstellar medium
• MOCCA: Effects of pristine gas accretion and cluster migration on globular cluster evolution, global parameters, and multiple stellar populations
• Indicatives of Early Stages of Star Formation in the Universe