Using Gamma-Ray Bursts' Pulses for Large-Scale Population Analysis
thesisposted on 2019-09-04, 13:46 authored by Alexander Amaral-Rogers
The current paradigm of GRB light curves is that the totality of the gamma-ray prompt emission can be modelled by the presence of either a single pulse, or by a series of convolved pulses, which rapidly decay before the onset of an X-ray afterglow. These pulses are well studied; but are popularly modelled by empirical functions which do not relate the spectral and temporal properties of the pulse as a unified whole. In this thesis we utilise a physically motivated model of pulse emission, that incorporates both spectral and temporal behaviour, to t the light curves of a significant proportion of all Swift observed GRBs with known associated redshifts; the X-ray afterglows observed by the Swift X-Ray Telescope are also fitted, using an empirical model, resulting in GRB light curves which are completely parameterised. We produce, with this data, an exhaustive GRB pulse and afterglow catalogue, and investigate some of the most commonly observed relationships between the fundamental GRB parameters. In Chapter 3 of this thesis we investigate the GRB luminosity distribution, utilising the large GRB pulse dataset of Chapter 2, in order to significantly improve our GRB population statistics. We produce, instead, a GRB pulse luminosity function for which the traditional GRB luminosity function can be considered as the high-luminosity tail. Given that the GRB luminosity distribution has been well studied, and has lead to assertions of evolution in observed GRB characteristics over cosmological timescales, we evaluate many of these models using our expanded dataset, and constrain more tightly the aforementioned luminosity function parameters. This, in turn, has allowed us to investigate some of the more common GRB progenitor model theories, and to indicate which models are more favourable in reproducing the observed behaviour of GRBs.