Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...19410503f&link_type=abstract
American Astronomical Society Meeting 194, #105.03
Astronomy and Astrophysics
Astronomy
Scientific paper
We apply a technique developed for fitting the observed energy distributions of main sequence B stars with stellar atmosphere models to a sample of lightly reddened early A-type stars. The technique utilizes an expanded grid of R.L. Kurucz's ATLAS 9 models and involves simultaneously determining all the parameters of the best fitting model (effective temperature, surface gravity, metallicity, and microturulence velocity) AND the properties of interstellar extinction (E(B-V) and, sometimes, the shape of the UV extinction curve). For the B stars it has been shown that the models reproduce the observed energy distributions to a level consistent with the expected observational uncertainties (for IUE satellite UV spectrophotometry and optical photometry). For the A stars, excellent agreement between models and observations is seen in the wavelength range longward of 1500 A. At shorter wavelengths the models tend to slightly overestimate the emergent flux. We discuss the possible reasons for this phenomenon and illustrate the quality of the fits for a number of A0 V to A3 V stars. The UV opacity in the A stars is dominated by absorption due to many thousands of Fe lines which produce a very distinct opacity signature, visible even in relatively low resolution data. We demonstrate the ability of the fitting procedure to exploit this spectral structure and provide precise and robust estimates of [Fe/H] from low-resolution UV spectrophotometry. Several examples, spanning a factor of nearly 20 in Fe abundances, are shown.
Fitzpatrick Edward L.
Massa Derck
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