COLOR EXCESSES FROM SIX-COLOR PHOTOMETRY OF SUPERGIANT STARS

Abstract

Although the supergiants are very rare objects, their high luminosity permits us to see and investigate considerable numbers of them in spite of the loss of light caused by their great distances and by the presence of absorbing material. Supergiants can be identified with considerable accuracy from their spectral characteristics. These stars, however, are almost always reddened. Because of their visibility, their tendency to delineate portions of galaxies composed of stars of Baade's Population I, their close kinship with the classical cepheid variables, and many other reasons, it is important to know the intrinsic colors and hence the color excesses of the supergiant stars. It is the purpose of this paper to study the possibilities of accomplishing this end by means of an application of multicolor photometry ; the procedure is similar to that followed previously by Becker1 and by Johnson and Morgan.2