Date of Completion
Honors College Thesis
Joanna M. Rankin
pulsar, neutron star, radio, astronomy, astrophysics, arecibo
A pulsar is a rapidly-rotating, highly magnetized neutron star which emits electromagnetic radiation, and has a rotational axis that is tilted from its magnetic axis. This discrepancy causes the radiation to sweep across the line-of-sight of our radio telescopes as the star rotates, separating the radiation into discrete pulses. Some pulsars exhibit episodes of “nulls”, defined to be groups of consecutive pulses with drastically reduced pulse-power. The standard hollow-cone emission model lacks a way to adequately describe these nulls. This observation has led to the development of the partially-filled-cone emission model. The goal of my research has been to determine empirically if the partially-filled-cone emission model is an improvement over the standard hollow-cone model in explaining the observed emission characteristics of pulsars B0751+32 and B0525+21. The characteristic fit of these pulse-sequences to both models has been accomplished using the following analytic methods: Colourplot, variation in pulse energy diagrams, average pulse profiles, average null profiles, null histograms, null-length histograms, burst-length histograms, longitude-resolved fluctuation spectra, pulse-modulation quelling, null-threshold comparisons, and analysis of expected single pulses preceded and followed by a null. These analyses have revealed conclusive evidence of null-periodicity in both stars, supporting the application of the partially-filled-cone model. However, because of the absence of partial nulls, and the presence of periodicities that appear in only a single component, it is not clear that either model can be used to adequately describe all features of the collected data.
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Orfeo, Daniel Jerome, "Periodic Nulls in Pulsars B0751+32 and B0525+21" (2014). UVM Honors College Senior Theses. 16.