Blue Straggler Stars: setting up a dynamical clock for open clusters

Abstract

Blue straggler stars are late bloomers that are bluer and brighter than the main sequence turnoff stars on a color-magnitude diagram of a cluster. Being a massive population compared to their other cluster siblings, their sedimentation level has been used to probe the dynamical evolution of globular clusters. In a series of studies, we explored the dynamical evolution of old open clusters, for the first time, making use of this same trait of the BSS that they settle quicker in the cluster core than any other cluster population. In these works, we have compared the theoretical estimation of dynamical ages, Nrelax, with the observed signatures of blue straggler stars segregation either by placing open clusters in Family I/II/III classification of dynamical ages defined in globular clusters or by estimating the area enclosed between the cumulative radial distributions of BSS and another reference population in 23 open clusters.