A search for detached white-dwarf/main-sequence binary stars in Omega Centauri

Observations of the globular cluster Omega Centauri taken with the Ultraviolet- Visible channel of the Wide Field Camera 3 (WFC3/UVIS) on the Hubble Space Telescope are used to detect some of the first candidate white-dwarf/main-sequence binaries in a globular cluster. In color-magnitude diagrams, white-dwarf/main-sequence binaries occupy the region between the white-dwarf sequence and the main sequence which, in the absence of high-quality proper-motion measurements, is also populated by main-sequence halo stars. We demonstrate that color-color diagrams can be used to distinguish background main-sequence stars from cluster white-dwarf/main-sequence binaries. This work is aimed at helping to elucidate the complex evolutionary and dynamical histories of binary stars in globular clusters by estimating the white-dwarf binary fraction for a globular cluster.