相关论文: Barium isotopic ratios in metal-poor stars: calibr…
We derive the mixture of odd to even barium isotopes in the atmosphere of the metal-poor subgiant HD140283 from the analysis of the Ba II transition at 455.4 nm in a high-resolution high signal-to-noise spectrum of the star. The detailed…
The [Ba/Eu] abundance ratio is commonly adopted as a tracer of the relative contributions of the slow (s) and rapid (r) neutron-capture processes. However, at [Fe/H] < -2 dex, Ba can be produced efficiently by both processes, rendering…
The measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic…
Current theory regarding heavy element nucleosynthesis in metal-poor environments states that the r-process would be dominant. The star HD140283 has been the subject of debate after it appeared in some studies to be dominated by the…
We provide measurements of the Ba isotopic fractions for five metal-poor stars derived with an LTE analysis using 1D model stellar atmospheres. We use high resolution (R\equiv{\lambda}/\Delta{\lambda}=90000-95000), very high signal-to-noise…
Heavy-elements, i.e. those beyond the iron peak, mostly form via two neutron capture processes: the s- and r-process. Metal-poor stars should contain fewer isotopes that form via the s-process, according to currently accepted theory. It has…
Barium stars are s-process enriched giants. They owe their chemical peculiarities to a past mass transfer phase. During which they were polluted by their binary companion, which at the time was an AGB star, but is now an extinct white…
The variations of elemental abundance and their ratios along the Galactocentric radius result from the chemical evolution of the Milky Way disks. The $\rm ^{12}C/^{13}C$ ratio in particular is often used as a proxy to determine other…
Magnesium (Mg) isotopic ratios offer valuable insights into stellar nucleosynthesis and Galactic chemical evolution, particularly in distinguishing contributions from supernovae and asymptotic giant branch (AGB) stars. These isotopes are…
Isotopic ratios of heavy elements are a key signature of the nucleosynthesis processes in stellar interiors. The contribution of successive generations of stars to the metal enrichment of the Universe is imprinted on the evolution of…
We have updated the Ba II model atom by taking into account the H I impact excitation with the rate coefficients from the quantum-mechanical calculations of Belyaev and Yakovleva (2018). Using high-resolution stellar spectra and the…
Analyses of the abundances of neutron-capture elements have led to the belief that these elements in metal-poor stars are r-process products with relative abundances closely resembling those found in the solar system. This picture was…
Barium stars show enhanced abundances of the slow neutron capture (s-process) heavy elements, and for this reason they are suitable objects for the study of s-process elements. The aim of this work is to quantify the contributions of the…
Abundances of heavier elements (barium and beyond) in many neutron-capture-element-rich halo stars accurately replicate the solar system r-process pattern. However, abundances of lighter neutron-capture elements in these stars are not…
Un-evolved, very metal-poor stars are the most important tracers of the cosmic abundance of lithium in the early universe. Combining the standard Big Bang nucleosynthesis model with Galactic production through cosmic ray spallation, these…
We present the Ba even-to-odd isotope abundance ratios in 25 cool dwarf stars with the metallicity [Fe/H] ranged between 0.25 and --1.35. Our method takes advantage of the hyperfine structure (HFS) affecting the \ion{Ba}{ii} resonance line…
The new generation of 3D hydrodynamical model atmospheres have been employed to study the impact of a realistic treatment of stellar convection on element abundance determinations of globular cluster stars for a range of atomic and…
The measurement of the cosmic microwave background has strongly constrained the cosmological parameters of the Universe. When the measured density of baryons (ordinary matter) is combined with standard Big Bang nucleosynthesis calculations,…
Context. Theoretical results showed the possibility that neutron capture elements were produced in the early Universe by two different sources: a frequent s-process source hosted by rotating massive stars, and a rare r-process source hosted…
A classical Local Thermodynamic Equilibrium analysis, based on high-resolution spectroscopic data, is performed for a sample of three potential barium dwarf candidates and one star already recognized as such. We derived their atmospheric…