Blue Straggler Stars in Galactic Open Clusters and the Simple Stellar Population Model

Blue straggler stars present as secure members in the Galactic open clustersform a major challenge to the conventional picture of evolutionary populationsynthesis based on the stellar evolution theory of single stars, as illustratedin our previous work. Expansion of our sample in the current work to includeyounger age clusters provides a larger data base to expose the question raisedfor the simple stellar population model. The working sample now includes 97Galactic open clusters of ages ranging from 0.1 to several Gyrs. Thecontributions of blue straggler stars to the integrated light of the hostclusters are calculated on an individual cluster base. A data base ofobservational constrained simple stellar population model is made which has alarger age coverage than our previous work. It is shown in this work that thegeneral existence of blue stragglers in star clusters of our sampledramatically altered the predictions of convectional stellar population modelin terms of spectral energy distribution. The integrated spectral energydistributions of the synthetic spectra of the clusters are enhanced towardsshorter wavelengths, therefore the results of the present work will cast newlights in understanding the properties of stellar populations.Comment: 27 pages, 8 figures, 1 table, submitted to Ap