Observations of low-mass stars in the Pleiades - Has a pre-main sequence been detected

BVRIJHK photometry and spectroscopy observations of a large sample of faint, proper motion low-mass stars in the Pleiades cluster are presented. Data indicate that a significant amount of these stars seem to lie on the main sequence with at least 17 m. Another sequence, in the magnitude range 15.0-17.5 m, is displaced along the main sequence by a Delta V of approximately 0.7. In comparing both sequences, it appears that the brighter sequence is more likely to be composed of binaries rather than pre-main-sequence stars. This interpretation, if correct, would imply that pre-main-sequence contraction time scales for solar masses of approximately 0.3 are incorrect by a factor of at least five.