UBC Theses and Dissertations
The detectability of millisecond pulsars in eccentric binary systems Madsen, Erik
With new, highly sensitive telescopes, increased computational power, and improved search algorithms, the present century has seen a great increase in the discovery of pulsars in globular clusters. These are typically fast-spinning 'millisecond' pulsars, and more often than not they are members of binary systems. Unlike in the Galactic field, millisecond pulsars in globular clusters are often found in eccentric systems because of disruptions and exchanges due to the high stellar density of the cluster environment. A long-standing problem is that of characterizing our sensitivity to pulsars in binary systems, particularly those with non-zero eccentricity. A pulsar's orbital motion modulates its observed pulse period, making its detection through standard Fourier analysis difficult or impossible. A common technique to mitigate this problem is the 'acceleration search', which corrects for uniform line-of-sight acceleration, but not higher-order variations. This is often a valid approximation, and many pulsars have been found this way. However, it is not clear where such a search breaks down. This is a problem with a many-dimensional phase space that includes all of the binary parameters, the pulsar parameters, and the various search inputs. Past studies have approached the problem analytically, and have made valuable insights; however, until recently they have been restricted to circular orbits, and have not accounted for pulsar brightness or signal digitization. Here I approach the problem empirically. I simulate 1.8 million pulsars in a variety of orbital configurations and explore the frequency of pulsar recovery across various dimensions of the phase space. I find in particular that, at very short orbital periods, high eccentricities make binary systems easier to detect.
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