NGC 7654: An interesting cluster to study star formation history ?

CCD UBV IC photometry in a wide eld around the open cluster NGC 7654 has been carried out for 17 860 stars, down to V 20. The reddening across the cluster region is found to be variable with E(B V )min = 0:46 to E(B V )max =0 :80. The cluster is situated at a distance of 1380 70 pc. The colour magnitude diagrams show a large age spread in the ages. Star formation was biased towards relatively higher masses during the early phase of star formation whereas most of the low mass stars of the cluster were formed during the later phase. The star formation seems to have been a gradual process that proceeded sequentially in mass and terminated with the formation of most massive stars. The present data do not support a uniform mass function (MF) for dierent regions in the cluster. Although for the whole cluster region, the MF in the observed mass range 0:8 M 4:5, can be represented by a single power law with a slope = 1:400:07, however it indicates various features when examined carefully. In three subregions of the cluster the slope , for the mass range 1:5 mass segregation in the cluster.