A High Sensitivity Pulsar Search.
Russell A Hulse · Scholarworks (University of Massachusetts Amherst) · 1975
This dissertation concerns the planning, implementation, and results from a highly sensitive, automated search for new pulsars. This research effort was begun with a study of the relevant signal detection theory, and the conclusions reached are presented. The general procedures developed were specifically tailored for use on a high speed minicomputer, and produced a search relatively free from observational selection effects. The actual computer coding of these procedures is also described, with emphasis on how the required speed and efficiency of these routines was obtained. The final system applied over half a million different matched digital filters to the data obtained from each successive telescope beam area. These filters correspond to a similar number of discrete combinations of possible pulsar parameters, within the approximate bounds: 0 ≤ DM ≤ 1280 cm-3 pc, 0.033< P <3.9 s, and 0.016< (w/P) <0.125. Here DM is the dispersion measure to the pulsar (the column density of free electrons), P is the pulsation period, and (w/P) is the ratio of pulse width to period, or duty cycle. Use of this search system at the 1000 foot telescope of the Arecibo Observatory resulted in the detection of 50 pulsars, 40 of which were not previously known. Parameters are presented for these new pulsars. The relatively limited range in dispersion measure exhibited by this pulsar sample is used, along with other evidence, to infer a reduced number density of pulsars at distances beyond approximately 10 kpc from the galactic center.