Abundance Ratios in Barium Stars

Barium even-to-odd isotope abundance ratios in thick disk and thin disk stars

We present the Ba even-to-odd isotope abundance ratios in 25 cool dwarf stars with the metallicity [Fe/H] ranging between 0.25 and –1.35. Our method takes advantage of the hyperfine structure (HFS) affecting the Ba  resonance line of the odd isotopes. The fractional abundance of the odd isotopes of Ba is derived from a requirement that Ba abundances from the resonance line λ 4554 and subordin...

Chemical abundance analysis of 19 barium stars

We aim at deriving accurate atmospheric parameters and chemical abundances of 19 barium (Ba) stars, including both strong and mild Ba stars, based on the high signalto-noise ratio and high resolution Echelle spectra obtained from the 2.16 m telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. The chemical abundances of the sample stars were obtained...

Abundance Ratios in the Oldest Stars

Magnesium 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...

Interpretation of abundance ratios

In this paper we discuss abundance ratios and their relation to stellar nucleosynthesis and other parameters of chemical evolution models, reviewing and clarifying the correct use of the observed abundance ratios in several astrophysical contests. In particular, we start from the well known fact that abundance ratios depend on stellar yields, initial mass function and stellar lifetimes and we s...