A UBV PHOTOMETRIC STUDY OF THE OPEN CLUSTER NGC 654.

Abstract

ABSTRACT Photographic UBV magnitudes and colors are presented for 83 stars in the region of the young open cluster NGC 654, which Stone (1977) determined to have nonzero membership probabilities. It is noted that one-third of these stars lie outside the cluster nuclear region, indicating the presence of a stellar corona. Further, the coronal stars can be used to investigate the known variable reddening in a cluster region much larger than considered in previous photometric studies. It is found that over the extended region, the reddening varies from E(B-V) = 0.77 to 1.13 magnitudes with several stars having larger reddenings, and a variable-extinction analysis gives an averaged absorption ratio of R = 2.9 + or - 0.6 (s.e.) which is in good agreement with an earlier study by Turner (1976). In addition, attention is given to the cluster H-R diagram, a study of the nuclear and coronal cluster regions, and a comparison of the cluster luminosity function with the Initial Luminosity Function of Sandage (1957).