| Popis: |
A chemical abundance analysis of a sample of 18 galactic field dwarf stars was performed with Kurucz (1993) stellar atmosphere models under Local Thermodynamic Equilibrium (LTE) assumptions. The abundance determinations were made using measurements of the 7771 Å oxygen triplet, several α-element lines, and numerous Fe lines. This study presents an examination of oxygen and α-element abundances as a function of age and metallicity. The trend of increasing [O/Fe] and [α/Fe] with age predicted by the standard model of chemical evolution is not observed. This suggests type Ia supernovae may not contribute to chemical evolution over the formation time of the halo, possibly due to type Ia supernovae onset times significantly longer than current models suggest or a halo formation model involving chemically isolated fragments with short duration star formation events. The [O/Fe] vs. [Fe/H] breakpoint is determined to be located near [Fe/H] -1.3 (within ∼ 0.2 dex), midway between previously suggested values of -1.0 and -1.7 dex. |
