Bibcode
Schonberner, D.; Herrero, A.; Becker, S.; Eber, F.; Butler, K.; Kudritzki, R. P.; Simon, K. P.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 197, no. 1-2, May 1988, p. 209-222.
Fecha de publicación:
5
1988
Número de citas
85
Número de citas referidas
72
Descripción
Spectrograms of a sample of nitrogen-rich early type stars (OBN stars)
are analyzed differentially to normal stars of similar spectral types by
means of NLTE methods. Effective temperatures, gravities and atmospheric
helium contents are derived by fitting theoretical profiles of hydrogen
and helium lines to the observations. The abundance analysis yields the
following striking result: All analyzed OBN stars have helium-enriched
atmospheres, the (number) fraction of helium being between 0.15 and
0.26. The normal stars have solar helim contents. The elemental
distribution of carbon, nitrogen and oxygen is also essentially solar in
the normal stars, but it is completely different in the atmospheres of
the OBN stars. Their nitrogen is enriched, carbon depleted, and oxygen
about normal.