Experiments with CP stars

Abstract

Described here is a preliminary and tentative application of a method for fine-classification of stars, selected for studies of galactic structure. The present investigation is based on about 100 stars within the approximate spectral type range B6-A5, for which both spectra andUBV photometry have been obtained.

The motivation of the project is the following: For the study of galactic fine-structure it is essential to use as many members as possible of stellar agglomerations of various type for a statistical treatment of the material. A-type stars are fairly numerous and reasonably bright, but if all chemically peculiar stars, fast rotators or multiple systems have to be omitted there is generally too little left for a relevant investigation. Here we perform some experiments in order to find a method for fine-classification of A stars, both normal and chemically peculiar, within the framework of the M K system.

In this connection it is desirable to reduce the present multitude of CP classifications to a manageable number. It is shown here that, independenttly of the definition of the degree of peculiarity, there is no sharp borderline separating the CP stars from the ‘normal’ ones.

Also it is found that spectral classification can on an average be performed with almost the same accuracy for CP stars as for the ‘normal’ ones provided cases of extreme peculiarity are avoided.