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dc.contributor.authorVandenBerg, Don A.
dc.contributor.authorBergbusch, Peter A.
dc.contributor.authorDotter, Aaron
dc.contributor.authorFerguson, Jason W.
dc.contributor.authorMichaud, Georges
dc.contributor.authorRicher, Jacques
dc.contributor.authorProffitt, Charles R.
dc.identifier.citationVandenBerg, Don A., Bergbusch, Peter A., Dotter, Aaron, Ferguson, Jason W., Michaud, Georges, Richer, Jacques, Proffitt, Charles R.. 2012. Models for Metal-Poor Stars with Enhanced Abundances of C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti, in Turn, at Constant Helium and Iron Abundances. Astrophysical Journal, v.755 no.1en_US
dc.descriptionClick on the DOI link below to access the article (may not be free).en_US
dc.description.abstractRecent work has shown that most globular clusters have at least two chemically distinct components, as well as cluster-to-cluster differences in the mean [O/Fe], [Mg/Fe], and [Si/Fe] ratios at similar [Fe/H] values. In order to investigate the implications of variations in the abundances of these and other metals for H-R diagrams and predicted ages, grids of evolutionary sequences have been computed for scaled solar and enhanced alpha-element metal abundances, and for mixtures in which the assumed [m/Fe] value for each of the metals C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti has been increased, in turn, by 0.4 dex at constant [Fe/H]. These tracks, together with isochrones for ages from approximate to 5 to 14 Gyr, have been computed for -3.0 <= [Fe/H] <= -0.6, with helium abundances Y = 0.25, 0.29, and 0.33 at each [Fe/H] value, using upgraded versions of the Victoria stellar structure program and the Regina interpolation code, respectively. Turnoff luminosity versus age re! lations from isochrones are found to depend almost entirely on the importance of the CNO cycle, and thereby mainly on the abundance of oxygen. Since C, N, and O, as well as Ne and S, do not contribute significantly to the opacities at low temperatures and densities, variations in their abundances do not impact the predicted T-eff scale of red giants. The latter is a strong function of the abundances of only Mg and Si (and Fe, possibly to a lesser extent) because they are so abundant and because they are strong sources of opacity at low temperatures. For these reasons, Mg and Si also have important effects on the temperatures of main-sequence stars. Due to their low abundances, Na, Ca, and Ti are of little consequence for stellar models. The effects of varying the adopted solar metals mixture and the helium abundance at a fixed [Fe/H] are also briefly discussed.en_US
dc.publisherIOP Publishingen_US
dc.relation.ispartofseriesAstrophysical Journal;v.755 no.1
dc.subjectGlobular clustersen_US
dc.subjectPhotometric systemen_US
dc.subjectSolar compositionen_US
dc.subjectRadiative accelerationsen_US
dc.subjectLuminosity functionsen_US
dc.subjectStellar Evolution Databaseen_US
dc.subjectGlobular-cluster starsen_US
dc.titleModels for metal-poor stars with enhanced abundances of C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti, in turn, at constant helium and iron abundancesen_US
dc.description.versionPeer reviewed
dc.rights.holderCopyright American Astronomical Society, 2012

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