Pulsars were first discovered in 1967 and since then the population has grown and expanded over several wavelengths. In this thesis three different X-ray pulsars and three black widow radio pulsars... Show morePulsars were first discovered in 1967 and since then the population has grown and expanded over several wavelengths. In this thesis three different X-ray pulsars and three black widow radio pulsars and their evolution has been examined. The pulsars in this work all show variability that was not expected of their type of sources, e.g. the pulsar 2A 1822-371 is found to have an orbital period that is expanding over time more than what is expected. We suggest this to be due to the pulsar being a super Eddington source. Another part of the thesis uncovers that the magnetic field may have a significant influence in the behavior of the pulsars. Low magnetic field pulsars often show a correlation between their pulse phase and their flux, whereas we find that this correlation is not present in high magnetic field pulsars. This could mean that the hot spot, where the pulsations origin, is not moving in high magnetic field pulsars but could be moving in low magnetic field pulsars. The first black widow pulsars discovered had unstable timing solutions, whereas the black widow pulsars in this work all have stable timing solutions, and we look into possible explanations to this difference. Show less
This thesis uses catastrophic stellar events (supernovae and stellar collisions) to investigate different aspects of their environment. The first part of the thesis examines what happens to... Show moreThis thesis uses catastrophic stellar events (supernovae and stellar collisions) to investigate different aspects of their environment. The first part of the thesis examines what happens to supernova remnants near supermassive black holes like the one in the Milky Way Galaxy. To do so, a technique is first developed for predicting the evolution of supernova remnants in non-uniform densities. This is used to demonstrate how supermassive black hole environments determine the evolution and lifetime of supernova remnants. Conversely, observations of supernova remnants can then be used to infer properties of the surroundings of supermassive black holes. Therefore, predictions are then given for the X-ray emission that could be observed from core-collapse supernova remnants in these regions. This emission can compete with other sources, such the accretion flow of the supermassive black hole itself. Next, the problem of a core-collapse supernova in a close binary system is considered, where the effect on the companion is studied to predict the properties of runaway stars from binaries disrupted after a supernova. Finally, simulations of blue stragglers, formed from stellar collisions, are used to learn about the globular clusters containing them. Estimating the collision times reveals details about the evolutionary history of the cluster. Show less
Red Dwarfs are at the heart of Astronomy because they are the most abundant type of star that we know of in our Galaxy. Yet, surprisingly little is known about their formation, evolution and the... Show moreRed Dwarfs are at the heart of Astronomy because they are the most abundant type of star that we know of in our Galaxy. Yet, surprisingly little is known about their formation, evolution and the nature of their companions. In this thesis I present the first results of the WFCAM Transit Survey, a unique long-time monitoring program of many thousands of red dwarfs in the infrared, where they are the brightest. By studying their properties in eclipsing binary systems it is shown that red dwarfs are of great value to simulations of low-mass star formation, binary dynamics, stellar structure and ultimately the fundamental properties of Earth-like planets. Show less
