Variability of accreting white dwarf binaries and other compact objects

Accreting white dwarf binaries, like cataclysmic variables (CVs) and AM~CVns, and other types of compact binaries are known to be highly variable in timescales of seconds to years. In the Galactic field, the existing big photometric surveys like ZTF and ASAS-SN have allowed for the discovery and study of the variability of these systems. This would only improve with upcoming surveys like the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Besides ground-based observatories, space-based missions like Kepler and TESS have also contributed immensely to the study of the variability and the detailed study of the outbursts from white dwarf binaries and other compact binaries in general. Using TESS in this dissertation, I showed how we can exploit the \emph{TESS} observing and timing capabilities to study accreting white dwarf binaries. I present the results of the first systematic study of outbursting AM~CVn systems and present for the first time strong limits on the duration and the morphology of the superoutbursts and normal outbursts in AM~CVns. I was also shown how \emph{TESS} can be used to help study other types of accreting white dwarf binaries like Cataclysmic Variables.

Sadly the same surveys cannot be used for dense stellar clusters, like globular clusters (GCs), due to crowding and limiting magnitudes. In the study of compact binaries in globular clusters the Hubble Space Telescope (HST) has revolutionized the field. In the more than 30 years of operations, HST observed numerous GCs, and the archive constitutes an invaluable resource. But there are still a lot of open questions regarding the population of compact binaries in GCs. Especially for the population of the, predicted, most abundant type of compact binaries, cataclysmic variables. I present the first results of an ongoing survey, which uses archival Hubble Space Telescope data of globular clusters with different characteristics, to do the first search for faint Cataclysmic Variables in Globular clusters that is not biased in the X-rays. I showed how this survey has helped to characterize other exotic binaries, such as obtaining the 2-day orbital period of a candidate redback pulsar in the globular cluster NGC 6397. This is the longest orbital period known for pulsars of that kind in any globular cluster. I will discuss the implications of that result. I also present the first results of the variability studied of other variables in the same globular cluster. Some results include the classification for the first time of two known CV candidates, the first magnetic He Core white dwarf candidate in globular clusters, and also the first detached white dwarf-red dwarf candidate in NGC~6397.