Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........1h&link_type=abstract
Ph.D. Thesis University of Western Ontario, London. Dept. of Astronomy.
Astronomy and Astrophysics
Astronomy
3
A Stars, Abundance, Peculiar Stars, Spectrum Analysis, Stellar Composition, Stellar Spectra, Data Reduction, Digital Simulation
Scientific paper
The abundances of 15 elements have been determined for 16 early A-type stars. Abundances were also determined for Sirius, a hot Am star, and lambda Boo, the prototypical member of its class. Spectrum synthesis was used to determine the abundances; it is shown to be reliable and capable of application to even broader lined stars. Despite the fact that 14 of the stars are classified as normal, they exhibit a considerable range of abundances. The abundances of most elements scale, at least roughly, with those of Fe, which ranges over more than 0.7 dex among supposedly normal stars. Carbon is probably anti-correlated with Fe while Ca exhibits a more complex behavior. Helium seems constant and slightly under-abundant with respect to the sun. Elements heavier than Fe generally show an enhancement with respect to the sun. Correlations of the abundances with various stellar parameters are studied. For some elements, such as Fe, the average abundance is roughly solar; for others, such as the heavy elements, it is not. The range of abundances exhibited by most elements is wide enough that there seems to be a continuous distribution of abundances from those of the Am stars through the normal stars. The lambda Boo stars may be the low abundance tail of this distribution.
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