Models of Metal-Poor Stars with Different Initial Abundances of C, N, O, Mg, and Si. I. Bolometric Corrections Derived from New MARCS Synthetic Spectra and Their Implications for Observed Colour-Magnitude Diagrams

Abstract

New, high-resolution MARCS synthetic spectra have been calculated for more than a dozen mixtures of the metals allowing, in turn, for variations in C:N:O, [CNO/Fe], and enhanced abundances of C, O, Mg, and Si. Bolometric Corrections (BCs) for many of the broad-band filters currently in use have been generated from these spectra. Due to improved treatments of molecules that involve atoms of C, N, and O, the BCs for UV and blue passbands, in particular, differ substantially from those derived from previous MARCS models. These differences, and the effects on BCs of varying the abundances of the metals, are shown in a number of instructive plots. Stellar evolutionary grids for -2.5 <= [Fe/H] <= -0.5 have also been computed for the different mixtures. Isochrones based on these tracks are intercompared on the theoretical H-R diagram and on a few of the colour-magnitude diagrams that can be constructed from HST Wide Field Camera 3 (WFC3) F336W, F438W, F606W, F814W, F110W, and F160W observations. For the first application of these models, isochrones have been fitted to WFC3 photometry of the globular cluster NGC 6496 from the HST UV Legacy Survey, with very encouraging results.

Accepted for publication in the MNRAS; the article consists of 20 pages, including 14 figures

References in corpus (21)

• Modules for Experiments in Stellar Astrophysics (MESA)
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• Carbon and oxygen abundances in stellar populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• Stellar Population Models and Individual Element Abundances I: Sensitivity of Stellar Evolution Models
• 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] $\le +0.4$
• On the primordial scenario for abundance variations within globular clusters. The isochrone test
• The State-of-the-Art HST Astro-Photometric Analysis of the core of ωCentauri. III. The Main Sequence's Multiple Populations Galore
• 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
• The HST Large Programme on NGC6752. II. Multiple populations at the bottom of the main sequence probed in NIR
• Four stellar populations and extreme helium variation in the massive outer-halo globular cluster NGC 2419
• Constraints on the distance moduli, helium and metal abundances, and ages of globular clusters from their RR Lyrae and non-variable horizontal-branch stars. II. Multiple stellar populations in 47Tuc, M3, and M13
• On the effect of helium enhancement on bolometric corrections and Teff-colour relations
• The Na-O anticorrelation in horizontal branch stars. V. NGC 6723
• Is helium the key parameter in the extended color spread of the first generation stars in M3?
• Models for Metal-Poor Stars with Different Initial Abundances of C, N, O, Mg, and Si. II. Application to the Colour-Magnitude Diagrams of the Globular Clusters 47 Tuc, NGC 6362, M5, M3, M55, and M92
• The effects of individual metal contents on isochrones for C, N, O, Na, Mg, Al, Si, and Fe
• Variable Stars in Metal-Rich Globular Clusters. IV. Long Period Variables in NGC 6496

Cited by in corpus (2)

• Models for Metal-Poor Stars with Different Initial Abundances of C, N, O, Mg, and Si. III. Grids of Isochrones for $-2.5\le$ [Fe/H] $\le -0.5$ and Helium Abundances $Y=0.25$ and $0.29$ at Each Metallicity
• Synthetic stellar spectra to study multiple populations in globular clusters: an extended grid and the effects on the integrated light