Blue Straggler Formation in Clusters

TL;DR

This paper reviews the formation mechanisms of blue stragglers in star clusters, emphasizing that both stellar collisions and binary mass transfer contribute, with their relative importance varying across different environments and cluster ages.

Contribution

It provides a comprehensive review of observational and theoretical studies on blue straggler formation, highlighting the dual role of collisions and binary evolution in clusters.

Findings

Both collision and binary mass transfer mechanisms are active.

The dominance of each mechanism varies with cluster environment.

Future research directions are suggested.

Abstract

Blue stragglers are thought to be formed from the merger or coalescence of two stars, but the details of their formation in clusters has been difficult to disentangle. We discuss the two main formation mechanisms for blue stragglers (stellar collisions or mass transfer in a binary system). We then look at the additional complications caused by the stars living in the dynamically active environment of a star cluster. We review the recent observational and theoretical work which addresses the question "which mechanism dominates?" and conclude that the most likely answer is that both mechanisms are at work, although with different importance in different environments and at different times in the cluster lifetime. We finish with a short discussion of some avenues for future work