Blue Straggler stars in Globular Clusters: Observations, Statistics and Physics

Christian Knigge (University of Southampton, UK)
 

All Galactic globular clusters (GCs) appear to host blue straggler stars (BSS). In principle, it should therefore 
be possible to infer the dominant mode of BSS formation in GCs statistically. For example, if most BSS are 
formed via dynamical interactions, the number found in a given cluster should correlate strongly with the 
expected collision rate in the cluster. Conversely, if most BSS are formed via mass transfer in binary 
systems, their number should scale with the number of binaries in the host cluster. In this contribution, I will 
review the long-standing search for such a "smoking gun" correlation, as well as related attempts to infer the 
formation mechanism(s) of BSS in GCs observationally. I will focus particularly on recent HST-based 
studies, some of which have had promising, yet not always mutually consistent results.