The fraction of binary systems in the core of 13 low-density Galactic globular clusters

We used deep observations collected with Advanced Camera for Surveys (ACS) at Hubble Space Telescope (HST) to derive the fraction of binary systems in a sample of 13 low-density Galactic globular clusters. By analysing the colour distribution of main-sequence stars we derived the minimum fraction of binary systems required to reproduce the observed colour–magnitude diagram morphologies. We found t...