Spectral
Energy Distributions and Physical Parameters
of the Atmospheres of Main-Sequence A Stars
with Infrared Excesses: Comparison with Normal Stars
I. N.
Glushneva*, V. I. Burnashev**, V. I. Shenavrin*, and S. S.
Guzii***
*Sternberg
Astronomical Institute, Universitetskii pr. 13, Moscow, 119899
Russia
**Crimean
Astrophysical Observatory, p/o Nauchnyi, Crimea, 334413 Ukraine
***Nikolaev
Pedagogical Institute, Nikolaev, Ukraine
Received June 17,
1996
Abstract—
For eight stars with infrared excesses greater than 0
5 in the IRAS bands, we obtained
the energy distribution over the range 3200–7600 Å and
measured their infrared JHKLM magnitudes. Similar
observations were performed for 21 stars of various subclasses of
the spectral type A with excesses no greater than 0
3. Based on the energy
distribution derived from the response curves of the photometric UBV
and WBVR systems, we computed the synthetic B–V
color indices, which are in good agreement with the photometric
observations. A comparison of the normalized energy distribution
in the spectra of A stars with infrared excesses greater than 0
5 in the IRAS bands and the mean
energy distribution for stars of the corresponding subclasses
shows that the maximum difference does not exceed 10% both in the
ultraviolet (3200–4000 Å) and in the near infrared (up to
7600 Å). In all of the stars studied, we detected no excesses in
the JHKLM bands that were greater than the accuracy of our
measurements. Using the method of infrared fluxes and comparing
the observed energy distribution with theoretical models of
Kurucz, we determined the effective temperatures and angular
diameters of the stars. For three stars, we estimated the
parameters of their dust shells.
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