Results 271 to 280 of about 85,308 (302)

Chemical Abundances in Stars

1988
The precise determination of chemical abundances in stars is the key to a number of important disciplines in modern astrophysics including stellar evolution and nucleosynthesis as well as the chemical and dynamical evolution of the Galaxy. The basic transport mechanisms in stellar atmospheres rule the observational aspects of stellar surfaces which are
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Chemical Abundances of Symbiotic Giants

EAS Publications Series, 2015
High resolution (R ∼ 50000), near-IR spectra were used to measure photospheric abundances of CNO and elements around the iron peak for 24 symbiotic giants. Spectrum synthesis was employed using local thermal equilibrium and hydrostatic model atmospheres. The metallicities are distributed in a wide range with maximum around [ Fe / H ] ∼−0.4 – − 0.3 dex.
C. Gałan, J. Mikołajewska, K.H. Hinkle, R.R. Joyce   +3 more
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Chemical Abundances in Meteorites

1988
Some 4.6 billion years ago contraction and subsequent collapse of an interstellar cloud led to the formation of the solar system. The ratio of heavy elements to hydrogen, increasing continuously in interstellar material, due to the addition of freshly synthesized material from stars, was frozen in for the solar system at this point of time.
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Chemical Abundances in Galaxies

1988
This article is intended as a brief overview of chemical abundances in galaxies other than our own. Attention is concentrated on global properties of ellipticals and spirals, and the methods by which abundances are estimated. References are predominantly to work which has appeared since the review of Pagel and Edmunds (1981).
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Chemical Abundances in Comets

1981
Photoelectric, filter photometry and spectrophotometry allow us to derive absolute abundances for a number of species in comets. Despite large differences in morphology, in gas-to-dust ratio, and in dynamical age, there appears to be remarkably little variation from comet to comet in the relative production rates of the species studied thus far.
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Stellar chemical abundances with the GHRS

Physica Scripta, 1996
The accurate quantitative analysis of high resolution ultraviolet spectra of ultra-sharp-lined early-type, chemically peculiar stars, obtained with the Goddard High Resolution spectrograph on the Hubble Space Telescope, has been made possible by the synergism between state-of-the-art astro-physics and state-of-the-art atomic spectroscopy. We illustrate
David S Leckrone, Sveneric Johansson, Glenn M Wahlgren, Charles R Proffitt, Tomas Brage   +4 more
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Chemical Abundances in Molecular Clouds

1987
At present approximately 70 interstellar molecules are known. We discuss methods for determining chemical abundances in interstellar clouds and present results for the best studied regions, which include the “spiral arm” clouds seen towards distant continuum sources, quiescent dark and giant clouds, and the gas in regions of active star formation.
W. M. Irvine, P. F. Goldsmith, Å. Hjalmarson   +2 more
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Unveiling the time evolution of chemical abundances across the Milky Way disc with APOGEE

Monthly Notices of the Royal Astronomical Society, 2023
B Ratcliffe, I Minchev, Tobias Buck
exaly  

Chemical Abundances in Old Populations

1992
Preliminary single-burst population synthesis models are presented for weak and strong spectral features as a function of metallicity for old populations. Models agree with published globular cluster observations as well as theoretical calibrations. For small ellipticals, the galaxies and model predictions agree well in all indices.
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A catalogue of planetary nebulae chemical abundances in the Galactic bulge

Monthly Notices of the Royal Astronomical Society, 2023
Q A Parker, A A Zijlstra, Parker Quentin A   +2 more
exaly