Outliers: multicolour photometry guiding the search for evolved binary systems in the globular cluster 47 Tucanae
Kepler, S. O.; Montgomery, M. H.; Winget, D. E.; Dreizler, S.; Piotto, G.; Dotter, A.; Nardiello, D.; Pelisoli, I.; Kamann, S.; Bellini, A.; Robinson, E. L.; Husser, T. -O.; Campos, Fabíola; Istrate, A. G.
United States, Brazil, Germany, United Kingdom, Italy
Abstract
We use Hubble Space Telescope multicolour photometry of the globular cluster 47 Tucanae to uncover a population of 24 objects with no previous classification that are outliers from the single-star model tracks in the colour-magnitude diagram and yet are likely cluster members. By comparing those sources with evolutionary models and X-ray source catalogues, we were able to show that the majority of those sources are likely binary systems that do not have any X-ray source detected nearby, most possibly formed by a white dwarf and a main-sequence star and a small number of possible double-degenerate systems.