The Formation and Role of Blue Straggler Stars in Open Clusters

The Formation and Role of Blue Straggler Stars in Open Clusters
Abstract: Blue straggler stars are rejuvenated core hydrogen-burning
stars that are bluer and brighter than the main sequence turnoff stars
of a cluster. They primarily form via mass transfer, merger, and
stellar collision. Recently formed post-mass transfer blue stragglers
exhibit significant UV excess in their spectral energy distributions.
Using UV-based multi-wavelength spectral energy distributions, we
detected low-mass to massive hot white dwarf companions to BSS and
their low-mass siblings in 2 open star clusters. Additionally, being
one of the most massive populations of star clusters, blue stragglers
experience a significant gravitational drag compared to other cluster
populations, leading to their faster segregation in the cluster
center.  This observational signature is a direct tool to assess the
dynamical status of star clusters. We estimated the relative
sedimentation level of the blue straggler population of 23 old open
clusters (ages > 1 Gyr) for the first time in the literature,
utilising various methods such as blue straggler stars' radial
distributions and estimating the area enclosed between the cumulative
radial distributions of blue straggler stars and other reference
populations. Finally, we estimate the dynamical ages of open clusters
by comparing empirical and theoretical parameters.