Gamma Ray Bursts: Selected results from the Swift mission.
thesisposted on 15.04.2009, 12:01 by Cheryl Pauline Hurkett
Gamma Ray Bursts (GRBs) are short, energetic events that mark the most violent explosions in the Universe. Current hypotheses associated them with the births of stellar-sized black holes or rapidly spinning, highly magnetized stars. The introduction to this work places GRBs in their historical and theoretical context and provides a description of the current models describing them. This study makes use of data from the Swift satellite. Chapter two is a multi-wavelength study of the high redshift GRB 050505, which indicates that this burst has properties consistent with the general lower z GRB sample. Furthermore there is evidence for a `jet-break' in the X-ray light curve; a phenomena rarely seen in Swift era bursts. The next two chapters investigate the presence of X-ray emission lines in GRB spectra. Chapter three provides a discussion of the pre-Swift observations and a comparison of three methods already extant in the literature for assessing the signiffcance of such spectral features. The detection limits for each method were determined for emission line strengths in bursts with spectral parameters typical of the Swift era sample. Chapter four applies these methods to a sample of 40 Swift bursts; no strong evidence was found for emission lines in early time X-ray spectra once host galaxy absorption was accurately modelled. Chapter five investigates the phenomena of `precursors' and `quiescent intervals', indicating a common origin for events normally ascribed to `prompt emission' and `flares', in line with previous studies, and extending it to cover `precursor' emission. Evidence was also found to reinforce (anti-)correlations seen between pulse temporal and energetic properties also seen in previous studies. The final chapter summarises the important results for each section and proposes future studies that could be conducted in each field.