Blue stragglers in open clusters. Part II

Abstract

We present the results of a spectroscopic study of blue straggler and main sequence B and A - type stars in the open clusters NGC 3496, NGC 6475, NGC 6633 and IC 2602. A detailed analysis based on Kurucz's atmosphere models showed that the main sequence stars rotate rather rapidly and differ from a normal (solar) metallicity for only a few light elements. The blue stragglers have significantly smaller projected rotational velocities. As a group, they show the same chemical peculiarities as ordinary cluster and galactic field stars of the same spectral type. Two blue stragglers and one main sequence star possess a rather low helium content. All investigated stars for which the carbon abundance could be measured showed a moderate-to-strong deficiency of this element. The phenomenon of the blue stragglers is briefly discussed on the basis of our study. Based on observations collected at European Southern Observatory.