Multi-wavelength studies of compact binaries

Binary stars with small orbits in which at least one of the components is a white dwarf, neutron star or a black hole are usually referred to as compact binaries. The presence of very large gravitational potentials in these systems offer the unique opportunity to study astrophysical phenomena under conditions that can never be achieved on Earth. Thanks to their excellent angular resolution and sensitivity, telescopes like Hubble and Chandra opened a new window in the study of compact binaries in crowded stellar environments such as globular clusters. Due to the high stellar interaction rates in clusters, it is expected that they harbour large populations of such compact binaries. However, their identification and study in globular clusters is very challenging. Only with multi-wavelength studies we can get new insights about their physics, formation and evolution. This thesis focuses on the study of compact systems which harbour white dwarfs and neutron stars. The combination of observations in optical, ultraviolet and X-rays in one cluster resulted in the discovery of several millisecond radio pulsar companions, tens of new cataclysmic variables and the second double degenerate candidate to date in any globular cluster. A comparison with the cataclysmic variables in other clusters was also carried out. An extensive X-ray study of a transient neutron star low-mass X-ray binary in another cluster revealed a different behavior to other neutron star transients. Additionally, the two confirmed transitional millisecond pulsars in the Galactic field were studied using mid-ultraviolet observations for the first time in this thesis.