The Isotopic Abundances of Magnesium in Stars
نویسندگان
چکیده
Isotopic abundance ratios Mg:Mg:Mg are derived for 20 stars from highresolution spectra of the MgH A-X 0-0 band at 5140Å. With the exception of the weak G-band giant HR 1299, the stars are dwarfs that sample the metallicity range -1.8 < [Fe/H] <0.0. The abundance of Mg and Mg relative to the dominant isotope Mg decreases with decreasing [Fe/H] in fair accord with predictions from a recent model of galactic chemical evolution in which the Mg isotopes are synthesised by massive stars. Several stars appear especially enriched in the heavier Mg isotopes suggesting contamination by material from the envelopes of intermediate-mass AGB stars. Subject headings: magnesium: stars: abundances:
منابع مشابه
The Chemical Evolution of Magnesium Isotopic Abundances in the Solar Neighbourhood
The abundance of the neutron-rich magnesium isotopes observed in metal-poor stars is explained quantitatively with a chemical evolution model of the local Galaxy that considers for the first time the metallicity-dependent contribution from intermediate mass stars. Previous models that simulate the variation of Mg isotopic ratios with metallicity in the solar neighbourhood have attributed the pr...
متن کاملMagnesium isotopic abundance ratios in cool stars
From high resolution spectra of 61 cool dwarfs and giants, Mg isotopic abundance ratios Mg:Mg:Mg are derived from spectral synthesis of the MgH A-X lines near 5140Å. Our sample spans the range −2.5 ≤ [Fe/H] ≤ 0.1, including the first measurements of Mg isotope ratios in stars with metallicities below [Fe/H]=−2.0. We confirm the decrease in Mg/Mg with decreasing [Fe/H] as predicted by recent mod...
متن کاملMagnesium Isotopes in Metal-Poor Dwarfs, the Rise of AGB Stars and the Formation Timescale of the Galactic Halo
We have determined magnesium isotopic ratios (Mg/Mg) in metal-poor (−2.6 ≤ [Fe/H] ≤ −1.3) halo dwarfs employing high S/N (90-280) high spectral resolution (R = 10) Keck HIRES spectra. Unlike previous claims of an important contribution from intermediate-mass AGB stars at low metallicities, we find that the rise of the AGB contribution in the Galactic halo did not occur until intermediate metall...
متن کاملAbundances of heavy metals and lead isotopic ratios in subluminous B stars
Abundances of heavy metals and lead isotopic ratios in subluminous B stars Abstract. We present a detailed abundance analysis of high-resolution ultraviolet echelle spectra of five subdwarf B stars obtained with HST-STIS The goal of our observations was to test the hypothesis that pulsations in sdBs are correlated to the surface abundances of iron-group elements. We study two pulsators and thre...
متن کاملEuropium Isotopic Abundances in Very Metal-poor Stars
Europium isotopic abundance fractions are reported for the very metal-poor, neutron-capture-rich giant stars CS 22892-052, HD 115444, and BD +17◦3248. The abundance fractions, derived from analysis of several strong Eu II lines appearing in high-resolution spectra of these stars, are in excellent agreement with each other and with their values in the Solar System: fr(Eu)≃ fr(Eu) ≃ 0.5. Detailed...
متن کامل