Special Type, Magnitude, and Color-Index Relations in the Galactic Star Cluster in Coma Berenices.

Abstract

view Abstract Citations (55) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Special Type, Magnitude, and Color-Index Relations in the Galactic Star Cluster in Coma Berenices. Weaver, Harold F. Abstract The Coma Berenices cluster is studied on the basis of new spectroscopic and photoelectric observations. Spectral types are assigned on the system of the Morgan, Keenan, and Keliman Atlas; a simple reliminary system of classifying metallic-line stars is proposed. Photoelectric magnitudes and co]ors, determined with both the 12-inch refractor and the 36inch Crossley reflector of the Lick Observatory, are compared with magnitudes and colors determined photoelectrically by Eggen and with magnitudes determined photographically by Trumpler. The magnitude-color, color-spectral-type, and -type diagrams determined from the new observational material are exhibited. From the first of these diagrams it appears that the majority of the fainter Coma stars (color range +0.2 to 0.6 mag.) form an extraordinarily compact sequence, in general agreement with Eggen's conclusion for these stars. However, some cluster members in this color range show much greater scatter from the compact sequence than can be accounted for by observational error. Application of a statistical test for the equality of variances shows that the scatter of the brighter main-sequence Coma stars (color <+0.2 mag.) about an empirical sequence line is almost, but not quite, significantly greater than the scatter observed for the fainter stars about an empirical sequence line. The stars in the upper part of the dwarf branch thus may form a less compact sequence than the fainter stars. The question of structure in the upper part of the diagram is considered in detail. It is shown that the statistical uncertainty introduced by cluster depth, observational error, and the small number of stars in the upper region of the main sequence prevents one from using the Coma cluster to determine any possible fine-structure details in the magnitude-color relation in this region of the diagram. Preliminary discussion of the metallic-line stars shows that these objects occur in the color-magnitude range of both normal A- and F-type stars. Spectral peculiarities among the brightest cluster members are briefly described; evidence is produced to show that main-sequence stars of the same color may have different spectral types on the basis of the customary -ratio criteria. The main sequence in the color-spectral-type diagram appears linear; the dispersion of the spectral type for a given observed color shows clearly. The -type diagram exhibits no new features in addition to those shown by the magnitude-color and color-spectral-type diagrams. Publication: The Astrophysical Journal Pub Date: November 1952 DOI: 10.1086/145653 Bibcode: 1952ApJ...116..612W full text sources ADS | data products SIMBAD (23)