Some Spectroscopic Characteristics of the OB Stars: an Investigation of the Space Distribution of Certain OB Stars and the Reference Frame of the Classification

Abstract

The distances of stars from the Victoria list of revised H7 spectrophotometric absolute magnitudes have been reinvestigated, by means of MK spectral classification at 63 Â mm-1. The two systems are compared with respect to spectral types, absolutè magnitudes, and space distribution of the individual stars; marked systematic and accidental differences are found to exist for the 09-B2 stars. The Victoria spectral types are systematically later, and the revised Victoria magnitudes consistently fainter, than those derived here. In terms of the present classifications, it is found that the OB stars investigated delineate the Local and Perseus spiral arms. Because the work was done with a dispersion approximately twice that of the MK atlas, the spectral classification has been investigated in detail. With a reference frame based upon ratios of the lines of helium and silicon, an increased classification resolution in the range 09-B1 is obtained. Also, a luminosity classification for the earlier O stars is proposed.