The Blue Stragglers and the Integrated Spectral Energy Distribution of Single Stellar Populations

Blue stragglers are a common observational fact for the Galactic clusters.Single Stellar Populations (SSPs)are basic to the studies of galaxy structre and evolution.SSPs are mainly based either on the observation of the integrated properties of star clusters, or on the theoretical understandings of single star evolution.Both of the two ways of making SSPs suffer from either observational uncertainties concerning field contaminations or lack of good models for close binary systems. Based on the photometry of the classical open cluster M67 and the thorough membership survey, we made a color-mag nitude diagram (CMD)of high membership stars for the cluster. We will show that by including the contributions of the bright blue stragglers that is common to open clusters, the integ rated properties of the clusters are quite different from tranditional SSP models.We further conclude that these blue light contributo rs are very important to SSP models, and may cast new lights on its applications in the studies of galaxies.