Abundance analyses of metal-poor stars. III. Red spectra of nine dwarfs
Logarithmic iron abundances with respect to the Sun are presented for HD 103095 (Groombridge 1830), HD 134440, HD 149414, BD +41/sup 0/3306, and BD -0/sup 0/4234, all cool, moderately to extremely metal-poor dwards, and HD 106516, HD 148816, BD +18/sup 0/3423, and HD 184499, solar-temperature dwarfs and subgiants of moderate metal deficiency. The model-atmosphere analysis is based on equivalent widths measured from photographic echelle spectra obtained with the 4 m telescope of Kitt Peak National Observatory. Emphasis is placed in the description of the analysis on the factors which most significantly affect its accuracy, namely, the measurement of equivalent widths of weak absorption features and the choice of solar and stellar parameters. Stellar equivalent widths of lines as weak as 10 mA have been used in this analysis, by invoking the goodness of the wavelength coincidence between observed and theoretical line positions to discriminate against noise features and line blends. Comparison with previous electrographic equivalent-width measurements suggests that a systematic error of as much as 4 mA may be present in the weak lines measured here, which may cause the stellar abundances in some cases to be as much as 0.1 dex too large. An error of comparable size is introduced due to uncertainties of +- 0.3 and +- 0.6 km s/sup -1/ in solar and stellar microturbulent velocities, respectively. Also presented is a rederivation of the iron abundances of 15 hotter, metal-poor dwarfs and subgiants analyzed previously, using choices of solar and stellar parameters that are consistent with this work, as well as furnace Fe I gf-values and an independently determined solar iron abundance, log (Fe/H) =-4.50. The latter approach produces abundances which are lower than the former by 0.2 dex; the discrepancy may be removed either by lowering solar and stellar microturbulent velocities to 0.7 km s/sup -1/ or by choosing log (Fe/H) =-4.70 for the Sun.
- Research Organization:
- Lockheed Palo ALto Research Laboratory
- OSTI ID:
- 5589597
- Journal Information:
- Astrophys. J.; (United States), Vol. 235:2
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
DWARF STARS
ENERGY SPECTRA
IRON
ABUNDANCE
CHEMICAL COMPOSITION
LINE WIDTHS
PHOTOGRAPHY
RADIAL VELOCITY
STELLAR ATMOSPHERES
SUN
ATMOSPHERES
ELEMENTS
MAIN SEQUENCE STARS
METALS
SPECTRA
STARS
TRANSITION ELEMENTS
VELOCITY
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
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