  Context. Blue Stragglers Stars (BSSs) are thought to form in globular
clusters by two main formation channels: i) mergers induced by stellar
collisions and ii) coalescence or mass-transfer between companions in binary
systems. The detailed study of the BSS properties is therefore crucial for
understanding the binary evolution mechanisms, and the complex interplay
between dynamics and stellar evolution in dense stellar systems. Aims. We
present the first comparison between the BSS specific frequency and the binary
fraction in the core of a sample of Galactic globular clusters, with the aim of
investigating the relative efficiency of the two proposed formation mechanisms.
Methods. We derived the frequency of BSSs in the core of thirteen low-density
Galactic globular clusters by using deep ACS@HST observations and investigated
its correlation with the binary fraction and various other cluster parameters.
Results. We observed a correlation between the BSS specific frequency and the
binary fraction. The significance of the correlation increases by including a
further dependence on the cluster central velocity dispersion. Conclusions. We
conclude that the unperturbed evolution of primordial binaries could be the
dominant BSS formation process, at least in low-density environments.
