Discovery and characterisation of transiting planets and low mass stars

Abstract

Transits offer us unique opportunities to study individual systems in great detail. This thesis presents discoveries of new transiting planets and low mass stars, and the characterisation of their fundamental properties: mass, radius, temperature, composition, and orbital dynamics. Ground-based surveys, like HATSouth, are successfully discovering the majority of characterisable transiting planets. The HATSouth survey is the only transit survey that operates a global network of telescopes, with identical setups, to search for transiting planets. The planets discovered by HATSouth orbit a diverse range of host stars, and the candidates identified have a wide range of orbital periods. However, a large number of planet candidates from ground-based surveys like HATSouth are stellar binary systems. We have developed an efficient reconnaissance follow-up program that identifies the astrophysical false positives and prioritises the best candidates for confirmation. All HATSouth planet discoveries are confirmed via this extensive follow-up campaign. We also introduce a series of low mass stars characterised by the HATSouth survey; the fundamental properties of which: mass, radius, temperature, are carefully measured to evaluate stellar evolution models for the most abundant stars in the galaxy. To characterise the atmospheres of the hot-Jupiter population, we use the Anglo-Australian Telescope to survey the near infrared secondary eclipses of nine hot-Jupiters. These observations represent some of the highest precision near-infrared time-series photometry performed from the ground, and probe a diverse range of hot-Jupiters. The secondary eclipse directly measures the day-side brightness temperatures of these planets. We find a diverse, but continuous distribution of spectral properties for the hot-Jupiter population. We explore this in the context of climate and global circulation in the atmospheres of these planets. We also present detections of sodium absorption, via transmission spectroscopy, for the hot-Jupiter WASP-17b. The shallower than expected depth of the sodium absorption suggests the presence of haze or ongoing photochemistry in the upper atmosphere of the planet.