Related papers: Clues on the Galactic evolution of sulphur from st…
We present here the first measurements of sulphur abundances in extragalactic stars. We make use of high resolution spectra, obtained with UVES at the ESO 8.2 m Kueyen telescope, of three giants of the Globular Cluster Terzan 7, which…
Sulfur abundances are derived for a sample of ten B main-sequence star members of the Orion association. The analysis is based on LTE plane-parallel model atmospheres and non-LTE line formation theory by means of a self-consistent spectrum…
The failure of S and O abundances in most planetary nebulae to display the same strong direct correlation that is observed in extragalactic H II regions represents one of the most perplexing problems in the area of PN abundances today.…
Aims: Aluminium is a key element to constrain the models of the chemical enrichment and the yields of the first supernovae. But obtaining precise Al abundances in extremely metal-poor (EMP) stars requires that the non-LTE effects be…
LTE and NLTE abundances of sulfur in 6 metal-poor giants and 61 dwarfs (62 dwarfs, including the Sun) were explored in the range of -3 \lsim [Fe/H] \lsim $+0.5$ using high-resolution, high signal-to-noise ratio spectra of the \SI 8693.9 \AA…
We have performed new determinations of sulphur and silicon abundances for a sample of 26 disk stars based on high-resolution, high signal-to-noise spectra. The results indicate a solar [S/Fe] for [Fe/H] >-0.3, below which [S/Fe] increases…
LTE abundances of light elements in extremely metal-poor (EMP) stars have been previously derived from high quality spectra. New derivations, free from the NLTE effects, will better constrain the models of the Galactic chemical evolution…
Aims: In this paper we aim to study the chemical evolution of sulphur in the galactic disk, using a new optimal abundance indicator: the [SI] line at 10821 A. Similar to the optimal oxygen indicators, the [OI] lines, the [SI] line has the…
Early chemical enrichment processes can be revealed by the careful study of metal-poor stars. In our Local Group, we can obtain spectra of individual stars to measure their precise, but not always accurate, chemical abundances.…
We present a methodology for the use of sulphur as global metallicity tracer in galaxies, allowing performing a complete abundance analysis using only the red-to-near infrared spectral region. We have applied it to a compilation of…
Sulphur is an element which is formed in the alpha-process and is easily measured in the gaseous phase in external galaxies. Since it does not form dust, it is the preferred indicator for alpha-elements, rather than Si or Mg, for which dust…
Metal-poor stars are crucially important for understanding the early Galaxy, first stars, and the Universe. In this series of papers, we present a homogeneous non-local thermodynamic equilibrium (NLTE) abundances analysis of 12 elements for…
Abundance ratios in extremely metal-poor (EMP) stars are a good indication of the chemical composition of the gas in the earliest phases of the Galaxy evolution. It had been found from an LTE analysis that at low metallicity, and in…
For the first time, we present an extensive study of stars with individual non-local thermodynamic equilibrium (NLTE) abundances for 17 chemical elements from Li to Eu in a sample of stars uniformly distributed over the $-2.62 \le$ [Fe/H]…
A chemical characterization of the Galactic Center is essential for understanding its formation and structural evolution. Trends of alpha-elements, such as Mg, Si, and Ca, serve as powerful diagnostic tools, offering insights into…
Following our solar work, we perform NLTE calculations of the Mn abundance for fourteen stars with [Fe/H] from 0 to -2.5, mainly to show how NLTE affects Mn abundances in cool stars of different metallicities.The spectrum synthesis and Mn…
We have developed a model atom for Cu with which we perform statistical equilibrium computations that allow us to compute the line formation of Cu I lines in stellar atmospheres without assuming Local Thermodynamic Equilibrium (LTE). We…
Based on the medium-high resolution (R~ 20,000), modest signal-to-noise ratio (S/N > 70) FLAMES-GIRAFFE spectra, we investigated the copper abundances of 129 red giant branch stars in the Galactic bulge with [Fe/H] from -1.14 to 0.46 dex.…
We review the present methodology for the use of Sulfur as global metallicity tracer in galaxies, which allows performing a complete abundance analysis using mainly the red to near infrared spectral region, and extending the range of…
We present the abundances of Li, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Zn, Sr, Y, Zr, and Ba in a wide metallicity range ($-2.8 \le$ [Fe/H] $\le -1.5$). Using the differential technique allowed us to obtain an unprecedented low…