The Color-Magnitude Diagram of the Pleiades Cluster Ⅱ

摘要

Two or three-color photographic and photoelectric photometry of virtually all of the known members of the Pleiades cluster is given. The photographic photometry was done on plates taken with the 13-inch telescope, while the photoelectric work was done with the 21-inch and 42-inch reflectors of the Lowell Observatory.nA sudden increase in the width of the main sequence is observed at V =12.0. This scatter may be associated with the probable fact that the fainter stars still in the process of gravitational contraction.nA “flare” of one faint Pleiades star was observed, and five other faint stars are thought also to be “flare” stars. It is suggested that the “flare” activity might be connected with the process of gravitational contraction of young late-type stars.