The Helium abundance and Delta Y / Delta Z in Lower Main Sequence stars

Abstract

We use nearby K dwarf stars to measure the helium-to-metal enrichment ratio, a diagnostic of the chemical history of the Solar Neighbourhood. Our sample of K dwarfs has homogeneously determined effective temperatures, bolometric luminosities and metallicities, allowing us to fit each star to the appropriate stellar isochrone and determine its helium content indirectly. We use a newly computed set of Padova isochrones which cover a wide range of helium and metal content. Our theoretical isochrones have been checked against a congruous set of main sequence binaries with accurately measured masses, to discuss and validate their range of applicability. We find that the stellar masses deduced from the isochrones are usually in excellent agreement with empirical measurements. Good agreement is also found with empirical mass-luminosity relations. Despite fitting the masses of the stars very well, we find that anomalously low helium content (lower than primordial helium) is required to fit the luminosities and temperatures of the metal poor K dwarfs, while more conventional values of the helium content are derived for the stars around solar metallicity. We have investigated the effect of diffusion in stellar models and LTE assumption in deriving metallicities. Neither of these is able to resolve the low helium problem alone and only marginally if the cumulated effects are included, unless we assume a mixing-length which is strongly decreasing with metallicity. Further work in stellar models is urgently needed. The helium-to-metal enrichment ratio is found to be Delta Y / Delta Z = 2.1 +/- 0.9 around and above solar metallicity, consistent with previous studies, whereas open problems still remain at the lowest metallicities. Finally, we determine the helium content for a set of planetary host stars.

arXiv comment29 pages, 13 figures, replaced to match published version in MNRAS

References in corpus (101)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Color Transformations for the 2MASS Second Incremental Data Release
• Constraining Cosmological Parameters Based on Relative Galaxy Ages
• Spectroscopic [Fe/H] for 98 extra-solar planet-host stars: Exploring the probability of planet formation
• Solar Models with Helium and Heavy Element Diffusion
• The effective temperature scale of FGK stars. II. Teff : color : [Fe/H] calibrations
• Theory of Low-Mass Stars and Substellar Objects
• Omega Centauri: The Population Puzzle Goes Deeper
• The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters
• Absolute dimensions of the M-type eclipsing binary YY Geminorum (Castor C): a challenge to evolutionary models in the lower main-sequence
• Abundances and Kinematics of Field Halo and Disk Stars I: Observational Data and Abundance Analysis
• The angular size of dwarf stars and subgiants - Surface brightness relations calibrated by interferometry
• Lithium isotopic abundances in metal-poor halo stars
• The Victoria-Regina Stellar Models: Evolutionary Tracks and Isochrones for a Wide Range in Mass and Metallicity that Allow for Empirically Constrained Amounts of Convective Core Overshooting
• Stellar Iron Abundances: non-LTE Effects
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• Abundances for metal-poor stars with accurate parallaxes I. Basic data
• S4N: A Spectroscopic Survey of Stars in the Solar Neighborhood
• A helium spread among the main sequence stars in NGC 2808
• Parent Stars of Extrasolar Planets VI: Abundance Analyses of 20 New Systems
• The Spite Lithium Plateau: Ultra-Thin but Post-Primordial
• Ages of Globular Clusters from Hipparcos Parallaxes of Local Subdwarfs
• Spectroscopic metallicities for planet-host stars: extending the samples
• Constraining solar abundances using helioseismology
• 10,000 Standard Solar Models: a Monte Carlo Simulation
• Implications of WMAP observations on Li abundance and stellar evolution models
• Solar-like oscillations in alpha Centauri B
• Revised Primordial Helium Abundance Based on New Atomic Data
• NEXXUS: A comprehensive ROSAT survey of coronal X-ray emission among nearby solar-like stars
• Standard Solar models in the Light of New Helioseismic Constraints II. Mixing Below the Convective Zone
• First stars VII. Lithium in extremely metal poor dwarfs
• The colours of the Sun
• The primordial abundance of 4He: a self-consistent empirical analysis of systematic effects in a large sample of low-metallicity HII regions
• New evidence for the complex struscture of the RGB of Omega Cen
• Accurate fundamental parameters for Lower Main Sequence Stars
• Are Standard Solar Models Reliable?
• On the correlation of elemental abundances with kinematics among galactic disk stars
• A Hipparcos study of the Hyades open cluster: Improved colour-absolute magnitude and Hertzsprung-Russell diagrams
• Constraining fundamental stellar parameters using seismology. Application to Alpha Centauri AB
• The Distances to Open Clusters from Main-Sequence Fitting. III. Improved Accuracy with Empirically Calibrated Isochrones
• The solar neighbourhood age-metallicity relation - does it exist?
• Abundances of refractory elements in the atmospheres of stars with extrasolar planets
• How much do helioseismological inferences depend upon the assumed reference model?
• The Solar Heavy Element Abundances: I. Constraints from Stellar Interiors
• A Large Stellar Evolution Database for Population Synthesis Studies. III. Inclusion of the full Asymptotic Giant Branch phase and Web tools for stellar population analyses
• Constraining the difference in convective blueshift between the components of alpha Cen with precise radial velocities
• Halo Star Lithium Depletion
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• Asteroseismology and calibration of alpha Cen binary system
• Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars
• The discrepancy between solar abundances and helioseismology
• Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third Edition - Comments and Statistics
• DY/DZ from fine structure in the Main Sequence based on Hipparcos parallaxes
• Why are the K dwarfs in the Pleiades so Blue?
• Stellar Mixing and the Primordial Lithium Abundance
• High resolution spectroscopy of metal rich giants in omega Cen: first indication of SNe Ia enrichment
• The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar-Type Stars
• On the Ages of Exoplanet Host Stars
• The Initial Helium Abundance of the Galactic Globular Cluster System
• Heavy Element Diffusion in Metal Poor Stars
• Metallicity effects on the chromospheric activity-age relation for late-type dwarfs
• Analysis of alpha Centauri AB including seismic constraints
• Rotational velocities of low-mass stars in the Pleiades and Hyades
• The cosmic production of Helium
• The Helium content and age of the Hyades: Constraints from five binary systems and Hipparcos parallaxes
• Further multiwavelength observations of the SSA22 Ly_alpha emitting `blob'
• A Consistency Test of Spectroscopic Gravities for Late-Type Stars
• Asteroseismic determination of helium abundance in stellar envelopes
• Discovery of an anomalous Sub Giant Branch in the Color Magnitude Diagram of omega Centauri
• Ages of globular clusters: a new approach
• Searching for Earth analogues around the nearest stars: the disk age-metallicity relation and the age distribution in the Solar Neighbourhood
• The Chemical Evolution of Helium
• Evolution of Deuterium, 3He and 4He in the Galaxy
• K dwarfs and the chemical evolution of the Solar cylinder
• The Distances to Open Clusters from Main-Sequence Fitting. I. New Models and a Comparison to the Properties of the Hyades Eclipsing Binary vB 22
• The Chemical Compositions of Stars with Planets: A Review
• Constraining the helium abundance with CMB
• Large-scale magnetic field of the G8 dwarf xi Bootis A
• Models of alpha Centauri A and B with and without seismic constraints: time dependence of the mixing-length parameter
• Hipparcos and the Age of the Galactic Disc
• Are beryllium abundances anomalous in stars with giant planets?
• ${}^7$Li Abundances in Halo Stars: Testing Stellar Evolution Models and the Primordial ${}^7$Li Abundance
• UV Bright Globular Clusters in M87: More Evidence for Super-helium-rich Stellar Populations?
• Stellar Structure and Evolution: Deductions from Hipparcos
• Atomic diffusion in metal-poor stars: II. Predictions for the Spite plateau
• Atomic diffusion in star models of type earlier than G
• An empirical calibration of the mixing-length parameter alpha
• Kinetic equilibrium of iron in the atmospheres of cool dwarf stars II. Weak Fe I lines in the solar spectrum
• Modelling the components of binaries in Hyades: The dependence of the mixing-length parameter on stellar mass
• Coronal Emission Measures and Abundances for Moderately Active K Dwarfs Observed by Chandra
• A Catalog of Helium Abundance Indicators from Globular Cluster Photometry
• A Physical Orbit for the High Proper Motion Binary HD 9939
• Asteroseismology of the visual binary 70 Ophiuchi
• On the effect of helium enhancement on bolometric corrections and Teff-colour relations
• The Distances to Open Clusters as Derived from Main-sequence Fitting. II. Construction of Empirically Calibrated Isochrones
• Disentangling discrepancies between stellar evolution theory and sub-solar mass stars. The influence of the mixing length parameter for the UV Psc binary
• Bias Properties of Extragalactic Distance Indicators.XI. Methods to Correct for Observational Selection Bias for RR Lyrae Absolute Magnitudes from Trigonometric Parallaxes Expected from the FAME Astrometric Satellite
• Detailed theoretical models for extra-solar planet-host stars: The "red stragglers" HD37124 and HD46375
• 85Peg A: which age for a low metallicity solar like star?

Cited by in corpus (79)

• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• Scaled solar tracks and isochrones in a large region of the Z-Y plane I. From the ZAMS to the TP-AGB end for 0.15 - 2.5 Mo stars
• Quantifying the uncertainties of chemical evolution studies. II. Stellar yields
• Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology
• Standing on the shoulders of Dwarfs: the Kepler asteroseismic LEGACY sample II - radii, masses, and ages
• Kinematics and history of the solar neighbourhood revisited
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• Fundamental Properties of Stars using Asteroseismology from Kepler & CoRoT and Interferometry from the CHARA Array
• New cooling sequences for old white dwarfs
• The second and third parameters of the Horizontal Branch in Globular Clusters
• A uniform asteroseismic analysis of 22 solar-type stars observed by Kepler
• M dwarfs: effective temperatures, radii and metallicities
• Age dissection of the Milky Way discs: red giants in the Kepler field
• Verifying asteroseismically determined parameters of Kepler stars using hipparcos parallaxes: self-consistent stellar properties and distances
• Properties of 42 Solar-type Kepler Targets from the Asteroseismic Modeling Portal
• A new determination of the local dark matter density from the kinematics of K dwarfs
• Magnetic Inhibition of Convection and the Fundamental Properties of Low-Mass Stars. I. Stars with a Radiative Core
• Stellar ages and convective cores in field main-sequence stars: first asteroseismic application to two Kepler targets
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• Li depletion in solar analogues with exoplanets: Extending the sample
• Stroemgren survey for Asteroseismology and Galactic Archaeology: let the SAGA begin
• Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs II: Properties of 11 T-dwarfs
• Helium enrichment and Carbon-star Production in Metal-rich Populations
• γ Doradus stars as test of angular momentum transport models
• What asteroseismology can do for exoplanets: Kepler-410A b is a Small Neptune around a bright star, in an eccentric orbit consistent with low obliquity
• On the alleged duality of the Galactic halo
• Determining the initial helium abundance of the Sun
• Helium abundance in a sample of cool stars: measurements from asteroseismology
• Cepheids in external galaxies. I. The maser-host galaxy NGC 4258 and the metallicity dependence of P-L and P-W relations
• ΔY/ ΔZ from the analysis of local K dwarfs
• A Tale of Two Anomalies: Depletion, Dispersion, and the Connection Between the Stellar Lithium Spread and Inflated Radii on the Pre-Main Sequence
• The Clusters AgeS Experiment (CASE). IV. Analysis of the Eclipsing Binary V69 in the Globular Cluster 47 Tuc
• An MCMC determination of the primordial helium abundance
• Tests and problems of the standard model in Cosmology
• The Gaia-ESO Survey: open clusters in Gaia-DR1 - a way forward to stellar age calibration
• Benchmark stars for Gaia: fundamental properties of the Population II star HD140283 from interferometric, spectroscopic and photometric data
• Asteroseismic modelling of solar-type stars: internal systematics from input physics and surface correction methods
• Testing pre-main sequence models: the power of a Bayesian approach
• Lithium-7 surface abundance in pre-MS stars. Testing theory against clusters and binary systems
• Kepler red-clump stars in the field and in open clusters: constraints on core mixing
• Constructing a one-solar-mass evolutionary sequence using asteroseismic data from \textit{Kepler}
• Evolution and colors of helium-core white dwarf stars with high-metallicity progenitors
• Angular Diameters of the G Subdwarf $\mu$ Cassiopeiae A and the K Dwarfs $\sigma$ Draconis and HR 511 from Interferometric Measurements with the CHARA Array
• Effect of Metallicity on the Evolution of the Habitable Zone from the Pre-Main Sequence to the Asymptotic Giant Branch and the Search for Life
• The detection and treatment of distance errors in kinematic analyses of stars
• The fate of the Antennae galaxies
• Uniform Forward-Modeling Analysis of Ultracool Dwarfs. I. Methodology and Benchmarking
• Gaia Gaps and the Physics of Low-Mass Stars. I. The Fully Convective Boundary
• HD 46375: seismic and spectropolarimetric analysis of a young Sun hosting a Saturn-like planet
• Five young $\delta$ Scuti stars in the Pleiades seen with Kepler/K2
• Variable Stars in the Cetus dSph Galaxy: Population Gradients and Connections with the Star Formation History
• Bayesian calibration of the mixing length parameter ${\alpha }_{ML}$ and of the helium-to-metal enrichment ratio $\Delta Y/\Delta Z$ with open clusters: the Hyades test-bed
• Asteroseismic modelling of solar-type stars: A deeper look at the treatment of initial helium abundance
• Hierarchically modelling Kepler dwarfs and subgiants to improve inference of stellar properties with asteroseismology
• Fundamental properties of nearby stars and the consequences on DeltaY/DeltaZ
• Modelling the accretion and feedback of supermassive black hole binaries in gas-rich galaxy mergers
• Modelling the solar twin 18 Sco
• A Concise Treatise on Converting Stellar Mass Fractions to Abundances to Molar Ratios
• The Baade-Wesselink p-factor applicable to LMC Cepheids
• On a new parameter to estimate the helium content in old stellar systems
• The distance to the young cluster NGC 7129 and its age
• Bridging the Gap between Intermediate and Massive Stars I: Validation of MESA against the State-of-the-Art Monash Stellar Evolution Program for a 2$M_{\odot }$ AGB Star
• From the stellar properties of HD219134 to the internal compositions of its transiting exoplanets
• Revisiting Delta Y/Delta Z from multiple main sequences in Globular Clusters: insight from nearby stars
• He abundances in disc galaxies -- I. Predictions from cosmological chemodynamical simulations
• Absolute dimensions of eclipsing binaries. XVII. A metal-weak F-type system, perhaps with preference for Y = 0.23-0.24
• Slow Magnetoacoustic Oscillations in Stellar Coronal Loops
• New models for the rapid evolution of the central star of the Stingray Nebula
• Evolution of Massive Stars along the Cosmic History
• Stellar evolution and modelling stars
• Energetic constraints to chemo-photometric evolution of spiral galaxies
• The PICS Project. I. The impact of metallicity and helium abundance on the bright end of the planetary nebula luminosity function
• Constraining the helium-to-metal enrichment ratio $\Delta Y/\Delta Z$ from main sequence binary stars. Theoretical analysis of the accuracy and precision of the age and helium abundance estimates
• Measurements of 4He in Metal-Poor Extragalactic HII Regions: the Primordial Helium Abundance and the Delta Y / Delta O Ratio
• Photometric stellar parameters for asteroseismology and Galactic studies
• Asteroseismic stellar modelling: systematics from the treatment of the initial helium abundance
• Application of Neural Networks to the study of stellar model solutions
• Asteroseismic analysis of red giants in eclipsing binaries using two methods: implications for scaling relations and chemical composition
• Galactic evolution of D, 3He and 4He