A search for time dependence in astrophysical neutrino sources with the Sudbury Neutrino Observatory

In this thesis I present the results of a periodicity study on the neutrino data collected over the span of the first two phases of SNO, at both low (1 day⁻¹ - 0.1 yr⁻¹) and high (1 day⁻¹ - 0.1 min⁻¹) frequency ranges. The high frequency study is the first of its kind, and is of particular interest in that it opens a window into the detection of solar g-mode oscillations, which have never been conclusively experimentally verified. In a data set with 7,646 neutrino candidates over a period of 698.29 live days, there was no detected high-frequency periodic signal. In addition to a wide-range, single-peak high-frequency search, I have performed a directed-region frequency analysis, and a noise-motivated broad-band analysis. All searches indicate an absence of periodicity in the 8B solar neutrino signal as measured by SNO. I have also carried out an analysis of time dependence in the context of a trigger-less burst search, with the motivation of either observing neutrinos from an optically occluded supernova, or setting an upper limit on the senstitivity of our detector for such an observation. I include discussions of backgrounds to such a search that are specific to a heavy-water Cherenkov detector such as SNO.