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A Radio-Frequency Study of Eclipsing Pulsar Binaries
[Thesis]. Manchester, UK: The University of Manchester; 2019.
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Abstract
In this thesis we present a detailed study into the poorly understood eclipse phenomena of Galactic field eclipsing pulsar binaries; known as the black widows and redbacks. The work is primarily based on a large set of radio-frequency observations, made up of both dedicated campaigns and archival data from a number of telescope facilities, in order to markedly increase the quality and volume of evidence to constrain future theoretical models, and as such, further our understanding. Here, we present the work in four interlinked parts: Firstly, we observed and investigated the eclipses of PSR J1810+1744, a near-unexplored black widow, at low-radio-frequencies. In this frequency domain the pulsar is bright, and the propagation effects that are vital to understanding the eclipse medium become more pronounced. Using these observations we constrain the mechanisms responsible for the eclipse and the mass loss rate from the companion star. Secondly, we performed an analysis of a well studied black widow, PSR J2051-0827, collating a large volume of data on its eclipses covering over a decade in time and frequencies from 100 MHz to 4 GHz. This time and frequency coverage is the most extensive used in a single dedicated eclipse study of a pulsar, and reveals variability in the eclipse phenomena on a range of timescales. Using observations sensitive to the polarisation of the pulsar radiation, we constrain the magnetic field strengths in the eclipse region. Stemming from our work on PSR J1810+1744, we conducted a dedicated low-frequency study of two more pulsars: redback PSR J1816+4510 and black widow PSR B1957+20. These two systems have similar orbital properties, however their companion stars differ in mass by nearly an order of magnitude. We compare the eclipse phenomena in both, finding remarkable similarities, seemingly independent of the companion masses. Finally, bringing together the four pulsars studied throughout this thesis, and adding a further redback - PSR J2215+5135 - we perform an analysis of the eclipse durations as a function of the pulsar radiation frequency. The results show that for all of the pulsars the eclipse widths scale inversely with frequency, however the rate at which they do so varies between systems. We discuss further complexities such as temporal variability of the eclipses and differing relationships acting at low- and high-frequencies.