On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models

Abstract

Stellar models have been computed for stars having [Fe/H] = 0.0 and -2.0 to determine the effects of using boundary conditions derived from the latest MARCS model atmospheres. The latter were fitted to the interior models at both the photosphere and at tau = 100, and at least for the 0.8-1.0 solar mass stars considered here, the resultant evolutionary tracks were found to be nearly independent of the chosen fitting point. Particular care was taken to treat the entire star as consistently as possible; i.e., both the interior and atmosphere codes assumed the same abundances and the same treatment of convection. Tracks were also computed using either the classical gray T(tau,T_eff) relation or that derived by Krishna Swamy (1966) to derive the boundary pressure. The latter predict warmer giant branches (by ~150 K) at solar abundances than those based on gray or MARCS atmospheres, which happens to be in good agreement with the inferred temperatures of giants in the open cluster M67 from the latest (V-K)-T_eff relations. Most of the calculations assumed Z=0.0125 (Asplund et al.), though a few models were computed for Z=0.0165 (Grevesse & Sauval) to determine the dependence of the tracks on Z_\odot. Grids of "scaled solar, differentially corrected" (SDC) atmospheres were also computed to try to improve upon theoretical MARCS models. When they were used as boundary conditions, the resultant tracks agreed very well with those based on a standard scaled-solar (e.g., Krishna Swamy) T(tau,T_eff) relation, independently of the assumed metal abundance. Fits of isochrones to the C-M diagram of the [Fe/H] = -2 globular cluster M68 were examined, as was the possibility that the mixing-length parameter varies with stellar parameters.

arXiv comment54 pages, including 20 figures and 3 tables; accepted (July 2007) for publication in the Astrophysical Journal

References in corpus (26)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• 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
• Low Temperature Opacities
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Towards Better Age Estimates for Stellar Populations: The Y^2 Isochrones for Solar Mixture
• Abundances for Globular Cluster Giants: I. Homogeneous Metallicities for 24 Clusters
• Homogeneous Photometry for Star Clusters and Resolved Galaxies. II. Photometric Standard Stars
• A standard stellar library for evolutionary synthesis: II. The M dwarf extension
• 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
• Updated Big Bang Nucleosynthesis confronted to WMAP observations and to the Abundance of Light Elements
• A probable stellar solution to the cosmological lithium discrepancy
• A Globular Cluster Metallicity Scale Based on the Abundance of Fe II
• Improved Color-Temperature Relations and Bolometric Corrections for Cool Stars
• Line formation in solar granulation VI. [C I], C I, CH and C2 lines and the photospheric C abundance
• A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
• Red Giant Branch stars: the theoretical framework
• 3D Hydrodynamical Simulations of Surface Convection in Red Giant Stars. Impact on spectral line formation and abundance analysis
• Element abundances of unevolved stars in the open cluster M 67
• A Study of the B-V Colour Temperature Relation
• Color transformations and bolometric corrections for Galactic halo stars: alpha-enhanced vs scaled-solar results
• Geometry of giant star model atmospheres: A consistency test
• A Constraint on Z_\odot from Fits of Isochrones to the Color-Magnitude Diagram of M67
• An empirical calibration of the mixing-length parameter alpha
• A pulsational approach to the luminosity of Horizontal Branch stellar structures
• Stellar models for very low mass main sequence stars: the role of model atmospheres

Cited by in corpus (43)

• The Dartmouth Stellar Evolution Database
• Improving PARSEC models for very low mass stars
• Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. II. age dependencies and new insights
• Stellar Models with Enhanced Abundances of C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti, in Turn, at Constant Helium and Iron Abundances
• Isochrones for Old (> 5 Gyr) Stars and Stellar Populations. I. Models for $-2.4\le$ [Fe/H] $\le +0.6$, $0.25\le Y\le 0.33$, and $-0.4\le$ [$\alpha$\Fe] $\le +0.4$
• Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. I. Measurements, methods, and first results
• On using the CMD morphology of M67 to test solar abundances
• Particle-physics constraints from the globular cluster M5: Neutrino Dipole Moments
• Age and mass of solar twins constrained by lithium abundance
• AmFm and lithium gap stars: Stellar evolution models with mass loss
• Effects of Helium Enrichment in Globular Clusters I.Theoretical Plane with PGPUC stellar evolution code
• Improvements to Stellar Structure Models, Based on a Grid of 3D Convection Simulations. I. $T(\tau )$-Relations
• On a new Near-Infrared method to estimate the absolute ages of star clusters: NGC3201 as a first test case
• Distance determination for RAVE stars using stellar models
• Lithium in M67: From the main sequence to the red giant branch
• Convection Theory and Sub-photospheric Stratification
• The age of 47Tuc from self-consistent isochrone fits to colour-magnitude diagrams and the eclipsing member V69
• Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters from their RR Lyrae and Non-Variable Horizontal-Branch Stars. I. M3, M15, and M92
• Constraining Globular Cluster Age Uncertainties Using the IR Color-Magnitude Diagram
• An Examination of Recent Transformations to the BV(RI)_C Photometric System from the Perspective of Stellar Models for Old Stars
• Effective temperatures of red giants in the APOKASC catalogue and the mixing length calibration in stellar models
• Stellar models with the ML2 theory of convection
• Red Giant evolution and specific problems
• Confronting uncertainties in stellar physics II. exploring differences in main-sequence stellar evolution tracks
• Surface convection and red giants radii measurements
• Testing stellar evolution models with the retired A star HD 185351
• On the Red Giant Branch: Ambiguity in the Surface Boundary Condition Leads to ~100 K Uncertainty in Model Effective Temperatures
• Multiple populations in massive star clusters under the magnifying glass of photometry: Theory and tools
• The Age of the Old Metal-Poor Globular Cluster NGC6397 Using WFC3/IR Photometry
• A model for redistributing heat over the surface of irradiated spider companions
• 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
• Population II stars and the Spite plateau; Stellar evolution models with mass loss
• On the determination of the He abundance distribution in globular clusters from the width of the main sequence
• Gas phase mean opacities for varying [M/H], N/O, and C/O
• Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. I. NGC 6940
• Star Cluster Ages in the Gaia Era
• Revisiting Delta Y/Delta Z from multiple main sequences in Globular Clusters: insight from nearby stars
• On the use of the main sequence knee (saddle) to measure globular cluster ages
• From Theory to Observations and viceversa: theoretical uncertainties and observational constraints
• Uncertainties and systematics in stellar evolution models of Red Giant Stars
• Benchmarking the effective temperature scale of red giant branch stellar models: the case of the metal-poor halo giant HD 122563
• Stellar models: firm evidence, open questions and future developments
• Influence of the Outer Boundary Condition on models of AGB stars