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The Occurrence of Abnormal Stars in Open Clusters

Published online by Cambridge University Press:  12 April 2016

Helmut A. Abt
Helmut A. Abt*
Affiliation:
Kitt Peak National Observatory

Abstract

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Morgan, Keenan, and others have found that low dispersions (80-130 Å mm-1) are ideal for obtaining spectral types and luminosity classes, especially for early-type stars. This is because at those dispersions certain blends are unresolved and remain useful, the hydrogen line wings are seen most clearly, and differences in rotational velocities are not so important. Such dispersions are also ideal or adequate for detecting some peculiarities, such as Am and Be spectra and some extreme Ap spectra, but they are inadequate for detecting abnormalities involving weak lines (as in Ap(Hg, Mn) stars) and line profiles (such as in shell spectra).

Type
II Criteria and Applications of MK Classification
Information
International Astronomical Union Colloquium , Volume 47: Spectral Classification of the Future , 1979 , pp. 95 - 98
Copyright
Copyright © Vatican Observatory 1979