The interior structure and evolution of blue straggler stars in open clusters.

Abstract

We present a detailed spectroscopic determination of effective temperatures and surface gravities of B- and A-type blue straggler stars in four open clusters by means of model atmospheres and new optical/UV spectrograms. By using a new method of analysis which also allows to separate objects not belonging to the cluster under investigation we show for the first time convincingly that blue stragglers are not the result of internal slow mixing processes as proposed by Wheeler (1979) and Saio & Wheeler (1980). Instead, their parameters are consistent with the predictions of normal stellar evolution. We discuss the implications of our result for possible evolutionary scenarios leading to straggling cluster stars.