Lithium in the lower red giant branch of 5 Galactic globular clusters

Abstract

Lithium is one of the few elements produced during the Big Bang Nucleosynthesis in the early universe. Moreover, its fragility makes it useful as a proxy for stellar environmental conditions. As such, the lithium abundance in old systems is at the core of different astrophysical problems. Stars in the lower red giant branch allow studying globular clusters where main sequence stars are too faint to be observed. We use these stars to analyze the initial Li content of the clusters and compare it to cosmological predictions, to measure spreads in Li between different stellar populations, and to study signs of extra depletion in these giants. We use GIRAFFE spectra to measure the lithium and sodium abundances of lower red giant branch stars in 5 globular clusters. These cover an extensive range in metallicity, from [Fe/H]$\sim -0.7$ to [Fe/H]$\sim -2.3$ dex. We find that the lithium abundance in these lower red giant branch stars forms a plateau, with values from $\mathrm{A}(\mathrm{Li}{)}_{\mathrm{NLTE}}=0.84$ to $1.03$ dex, showing no clear correlation with metallicity. When using stellar evolutionary models to calculate the primordial abundance of these clusters, we recover values $\mathrm{A}(\mathrm{Li}{)}_{\mathrm{NLTE}}=2.1-2.3$ dex, consistent with the constant value observed in warm metal-poor halo stars, the Spite plateau. Additionally, we find no difference in the lithium abundance of first and second population stars in each cluster. We also report the discovery of a Li-rich giant in the cluster NGC3201, with $\mathrm{A}(\mathrm{Li}{)}_{\mathrm{NLTE}}=1.63\pm 0.18$ dex, where the enrichment mechanism is probably pollution from external sources.

arXiv commentAccepted for publication in A&A

References in corpus (83)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Gaia Data Release 2. Summary of the contents and survey properties
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Planck 2013 results. XVI. Cosmological parameters
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• Multiple Stellar Populations in Globular Clusters
• Na-O Anticorrelation and HB. VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra
• The ACS Survey of Galactic Globular Clusters. VII. Relative Ages
• Gaia EDR3 view on Galactic globular clusters
• The Primordial Lithium Problem
• A new implementation of the infrared flux method using the 2MASS catalogue
• A library of high resolution synthetic stellar spectra from 300nm to 1.8 micron with solar and alpha-enhanced composition
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• NLTE line formation of Fe for late-type stars. I. Standard stars with 1D and <3D> model atmospheres
• The giant, horizontal and asymptotic branches of galactic globular clusters. I. The catalog, photometric observables and features
• Departures from LTE for neutral Li in late-type stars
• A probable stellar solution to the cosmological lithium discrepancy
• Implications of WMAP observations on Li abundance and stellar evolution models
• What is a globular cluster? An observational perspective
• The accretion of planets and brown dwarfs by giant stars -- II. solar mass stars on the red giant branch
• Signatures of intrinsic Li depletion and Li-Na anti-correlation in the metal-poor globular cluster NGC6397
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• Galactic Globular Cluster Relative Ages. II
• YREC: The Yale Rotating Stellar Evolution Code
• Accurate parameters of 93 solar-type Kepler targets
• New evidence for the complex struscture of the RGB of Omega Cen
• Massive AGB models of low metallicity: the implications for the self-enrichment scenario in metal poor Globular Clusters
• Production and evolution of Li, Be and B isotopes in the Galaxy
• Reappraising the Spite Lithium Plateau: Extremely Thin and Marginally Consistent with WMAP
• Standard big bang nucleosynthesis and primordial CNO Abundances after Planck
• Observational evidence for a broken Li Spite plateau and mass-dependent Li depletion
• M22: A [Fe/H] Abundance Range Revealed
• Homogeneous photometry VII. Globular clusters in the Gaia era
• The Lithium Content of the Galactic Halo Stars
• Uncloaking globular clusters in the inner Galaxy
• Li in NGC 6752 and the formation of globular clusters
• Models of Metal Poor Stars with Gravitational Settling and Radiative Accelerations: I. Evolution and Abundance Anomalies
• On Lithium-Rich Red Giants. I. Engulfment of Sub-Stellar Companions
• Lithium abundance in the globular cluster M4: from the Turn-Off to the RGB Bump
• GALA: an automatic tool for the abundance analysis of stellar spectra
• Early optical spectra of nova V1369 Cen show presence of Lithium
• Tidal interactions between binary stars drives lithium production in low-mass red giants
• Metal-Poor Lithium-Rich Giants in the Radial Velocity Experiment Survey
• Comparing CN and CH Line Strengths in a Homogeneous Spectroscopic Sample of 8 Galactic Globular Clusters
• TOPoS: IV. Chemical abundances from high-resolution observations of seven EMP stars
• Lithium-Rich Giants in Globular Clusters
• Lithium and sodium in the globular cluster M4. Detection of a Li-rich dwarf star: preservation or pollution?
• Lithium in the Globular Cluster NGC 6397: Evidence for dependence on evolutionary status
• Abundance Anomalies and Rotational Evolution of Low Mass Red Giants: A Maximal Mixing Approach
• Lithium-rich giants in the Galactic thick disk
• A chemical trompe-l'œil: no iron spread in the globular cluster M22
• Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tuc
• An Extremely Lithium-Rich Bright Red Giant in the Globular Cluster M3
• Back to the Lithium Plateau with J0023+0307 with [Fe/H]<-6
• Lithium and proton-capture elements in Globular Cluster dwarfs: the case of 47 Tuc
• The lithium content of omega Centauri. New clues to the cosmological Li problem from old stars in external galaxies
• Giants reveal what dwarfs conceal: Li abundance in lower RGB stars as diagnostic of the primordial Li
• Lithium abundances in globular cluster giants: NGC 1904, NGC 2808, and NGC 362
• Atomic diffusion and mixing in old stars VI: The lithium content of M30
• Facing the problems on the determination of stellar temperatures and gravities: Galactic globular clusters
• The role of lithium production in massive AGB and super--AGB stars for the understanding of multiple populations in Globular Clusters
• On the lithium content of the globular cluster M92
• Li - O anti-correlation in NGC 6752: evidence for Li-enriched polluting gas
• Influence of departures from LTE on calcium, titanium, and iron abundance determinations in cool giants of different metallicities
• Lithium and Beryllium in the Gaia-Enceladus Galaxy
• Mapping the differential reddening in globular clusters
• Lithium abundances in globular cluster giants: NGC 6218 (M12) and NGC 5904 (M5)
• The cosmological Lithium problem outside the Galaxy: the Sagittarius globular cluster M54
• A Census of Variability in Globular Cluster M68 (NGC 4590)
• Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters From Their RR Lyrae and Non-Variable Horizontal-Branch Stars. III. M55 and NGC 6362
• On the serendipitous discovery of a Li-rich giant in the globular cluster NGC 362
• The GALAH Survey: Accreted stars also inhabit the Spite Plateau
• The Gaia-ESO Survey: an extremely Li-rich giant in the globular cluster NGC 1261
• Lithium abundance in lower red giant branch stars of Omega Centauri
• Variability in NGC 3201 giant stars and its impact on their spectroscopic [Fe/H] determination
• The discovery of a Li-Na-rich giant star in Omega Centauri: formed from the pure ejecta of super-AGB stars?
• Lithium in NGC 2243 and NGC 104

Cited by in corpus (7)

• Constraints on the Cosmological Coupling of Black Holes from the Globular Cluster NGC 3201
• Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants
• Evidence of extra-mixing in field giants as traced by lithium and carbon isotope ratio
• Lithium in Kepler Red Giants: Defining Normal and Anomalous
• A combined study of thermohaline mixing and envelope overshooting with PARSEC: Calibration to NGC 6397 and M4
• Discovery of a Metal-Poor Red Giant Star with the Highest Ultra-Lithium Enhancement
• The true nature of HE0057-5959, the most metal-poor Li-rich star