Related papers: Light Elements in Main Sequence Stars: Li, Be, B, …
Essentially everything of astronomical interest is either part of a galaxy, or from a galaxy, or otherwise relevant to the origin or evolution of galaxies. Diverse examples are that the isotropic composition of meteorites provides clues to…
Some O and B stars show unusually strong or weak lines of carbon and/or nitrogen. These objects are classified as OBN or OBC stars. It has recently been shown that nitrogen enrichment and carbon depletion are the most likely explanations…
The first generation of stars was formed from primordial gas. Numerical simulations suggest that the first stars were predominantly very massive, with typical masses M > 100 Mo. These stars were responsible for the reionization of the…
Cosmic rays of kinetic energies below ~1 GeV per nucleon are thought to play a key role in the chemistry and dynamics of the interstellar medium. They are also thought to be responsible for nucleosynthesis of the light elements Li, Be, and…
The evolution and distribution of metals within galaxies are critical for understanding galactic evolution and star formation processes, but the mechanisms responsible for shaping this distribution remain uncertain. In this study, we carry…
High-resolution and high S/N CCD spectra were analyzed to determine accurate LTE abundances in four lambda Boo stars: pi^1 Ori, 29 Cyg, HR 8203 and 15 And. In general, 14 chemical elements were investigated. The main results are the…
We present a chemical abundance study of giant stars in the Galactic open cluster NGC 5822, which hosts two barium stars (#002 and #201) and three lithium-enriched giants (#006, #102, and #240). Using high-resolution optical and…
The earliest generation of stars, far from being a mere novelty, transformed the universe from darkness to light. The first atoms to form after the Big Bang filled the universe with atomic hydrogen and a few light elements. As gravity…
Elemental abundances are key to our understanding of star formation and evolution in the Galactic center. Previous work on this topic has been based on infrared (IR) observations, but X-ray observations have the potential of constraining…
We review recent observational studies of heavy element abundances in low metallicity stars and explore some implications of these results for nucleosynthesis and early Galactic chemical evolution.
Beryllium and oxygen abundances have been derived in a sample of F-type field stars for which lithium abundances had been measured previously, with the aim of obtaining observational constraints to discriminate between the different mixing…
As building blocks of dust, rocky planets, and even complex life, the chemical elements heavier than hydrogen (H) and helium (He) - called "metals" in astronomy - play an essential role in our Universe and its evolution. Up to Fe and Ni,…
Big Bang Nucleosynthesis is the theory of the production of the the light element isotopes of D, He3, He4, and Li7. After a brief review of the essential elements of the standard Big Bang model at a temperature of about 1 MeV, the…
Photospheric C, N, and O abundances of 118 solar-analog stars were determined by applying the synthetic-fitting analysis to their spectra in the blue or near-UV region comprising lines of CH, NH, and OH molecules, with an aim of clarifying…
The past few years have seen a steady progress in the determination of element abundances at high redshifts, with new and more accurate measures of metallicities in star-forming galaxies, in QSO absorbers, and in the intergalactic medium.…
We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch stars in two Galactic bulge fields centered near (l,b)=(+5.25,-3.02) and (0,-12). The (+5.25,-3.02)…
Initial conditions are set by Big bang nucleosynthesis from which we know that 90 per cent of baryons are dark and have essentially unknown chemical composition. In our own Galaxy, there are many clues from individual stars in different…
Many nucleosynthetic channels create the elements, but two-parameter models characterized by $\alpha$ and Fe nonetheless predict stellar abundances in the Galactic disk to accuracies of 0.02 to 0.05 dex for most measured elements, near the…
Li abundances in the bulk of low-mass metal-poor stars are well reproduced by stellar evolution models adopting a constant initial abundance. However, a small number of stars have exceptionally high Li abundances, for which no convincing…
Carbon is one of the most abundant metals in the universe because of its synthesis in the fundamental triple alpha reaction. The knowledge of carbon abundances in different environments is one key ingredient to our understanding of stellar…