Probing the time-resolved Universe

Studying the Universe in a time-resolved manner, including both high-speed variability, and transient events, allows us to explore the most extreme astrophysical environments. The study of transient astronomy and high-speed variability requires specialist instrumentation to explore the fastest timescales, and follow-up rapidly fading events. For this reason I have helped to develop two facilities for time-resolved astronomy, and used them to conduct two research programmes. In this thesis I present the lab-based and on-sky commissioning of the high-speed imager ultraspec. I include a theoretical analysis of the instrument throughput, and compare this with the observed throughput, finding that ultraspec is performing to within ∼ 20% of expectations in all filters. I also present a method for flux calibrating the non-standard KG5 filter, using bolometric corrections and model spectra of stellar atmospheres. I describe the design and operation of the 0.5m robotic telescope pt5m. I have developed a collection of software programmes which enable pt5m to function as an automated transient follow-up facility, which listens for new events and acts on them immediately, collecting and reducing the data. I present the results of performance tests, and scientific results from follow-up observations of transients such as GRBs, supernovae, and an outbursting X-ray binary. I then used pt5m to conduct a search for eclipsing cataclysmic variables, and further investigated the structure of their eclipses with ultraspec. I found or confirmed 13 new eclipsing systems, of which two are definitely suitable and six are possibly suitable for detailed modelling of their eclipse structure. I also used ultraspec, and later pt5m, to search for possible optical counterparts to recently discovered fast radio bursts (FRBs). FRBs are bright, short pulses of radio emission from unknown sources. I followed-up two FRB detections in detail, finding no evidence for counterparts in one field, but 5 variable sources in the other, all of which require further study.