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

dc.contributor.author	VandenBerg, Don A.
dc.contributor.author	Bergbusch, Peter A.
dc.contributor.author	Dotter, Aaron
dc.contributor.author	Ferguson, Jason W.
dc.contributor.author	Michaud, Georges
dc.contributor.author	Richer, Jacques
dc.contributor.author	Proffitt, Charles R.
dc.date.accessioned	2012-09-09T01:05:29Z
dc.date.available	2012-09-09T01:05:29Z
dc.date.issued	2012-08-10
dc.identifier.citation	VandenBerg, 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.1	en_US
dc.identifier.issn	0004-637X
dc.identifier.other	WOS:000306909500015
dc.identifier.uri	http://dx.doi.org/10.1088/0004-637X/755/1/15
dc.identifier.uri	http://hdl.handle.net/10057/5264
dc.description	Click on the DOI link below to access the article (may not be free).	en_US
dc.description.abstract	Recent 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.language.iso	en_US	en_US
dc.publisher	IOP Publishing	en_US
dc.relation.ispartofseries	Astrophysical Journal;v.755 no.1
dc.subject	Diffusion	en_US
dc.subject	Globular clusters	en_US
dc.subject	Photometric system	en_US
dc.subject	Solar composition	en_US
dc.subject	Radiative accelerations	en_US
dc.subject	Luminosity functions	en_US
dc.subject	Stellar Evolution Database	en_US
dc.subject	Globular-cluster stars	en_US
dc.title	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	en_US
dc.type	Article	en_US
dc.description.version	Peer reviewed
dc.rights.holder	Copyright American Astronomical Society, 2012