Exoplanet Discovery and Characterisation with the Next Generation Transit Survey

The breadth of parameter space spanned by the exoplanet population is vast and, as of yet, incomplete. In an effort to contribute new discoveries to the field, and to better-characterise the planets that are already known, an array of space and ground-based telescopes have been built in recent years. Amongst them is the Next Generation Transit Survey, or NGTS, a wide-field red-optimised facility based in the Paranal desert which aims to discover Neptune-sized planets around M and K dwarf hosts. 

In this thesis, I outline my work as part of the NGTS consortium. This includes my role in acquiring crucial follow-up transit data of 37 promising candidates at the South African Astronomical Observatory, the results of which have directly contributed to the confirmation of eight NGTS objects. In addition, I present new NGTS observations of the young, bright, multi-planet system AU Mic, and use Nested Sampling to produce a preliminary fit with TESS photometry. The resulting model is shown to be in accordance with recent literature, with the NGTS data poised to provide clarity on the much-disputed transit-timing-variations of AU Mic b.

Next, I detail the analysis of four newly-discovered gas giants from NGTS, which are found to be typical hot Jupiters orbiting main-sequence G-type stars. These objects make a valuable contribution to the growing population of highly-irradiated gaseous planets which often exhibit inexplicably large radii. I then continue to explore this topic of hot Jupiter inflation, identifying a region of parameter space in which some planets appear to exhibit an additional expansion. I undertake a systematic evaluation of planets in this regime to verify this observation, which in turn leads to preliminary conclusions about the physics which may underpin it. The identification of a new subset of ‘over-inflated’ hot Jupiters lays the foundation for a multitude of future studies.