CAOSP abstracts, Volume: 27, No.: 3, year: 1998
- Author(s): LEONE, F.
- Journal: Contributions of the Astronomical Observatory Skalnate Pleso,
vol. 27, no. 3, p. 285-289.
- Date: 04/1998
- Title: Helium in chemically peculiar stars
- Keyword(s): STARS: CHEMICALLY PECULIAR, ABUNDANCES: HELIUM
- Pages: 285 -- 289
Abstract:
For the purpose of deriving the helium abundances in chemically peculiar
stars, the importance of assuming a correct helium abundance has been
investigated for determining the effective temperature and gravity of main
sequence B-type stars, making full use of the present capability of
reproducing their helium lines. Even if the flux distribution of main
sequence B-type stars appears to depend only on the effective temperature
for any helium abundance, the effective temperature, gravity and helium
abundance have to be determined simultaneously by matching the Balmer line
profiles. New MULTI NLTE calculations, performed adopting ATLAS9 model
atmospheres and updated helium atomic parameters, reproduce most of the
observed equivalent widths of neutral helium linesfor main sequence B-type
stars and they make us confident of the possibility to correctly derive
the helium abundance in chemically peculiar stars. An application of previous
methods to the helium rich star HD 37017 shows that helium could be stratified
in the magnetic pole regions, as expected in the framework of the diffusion
theory in the presence of mass loss.
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