UBC Theses and Dissertations
Finding new pulsars using CHIME/FRB single pulse events Dong, Fengqiu
Pulsars are compact objects which are remnants of once-massive stars. Most are lighthouses in radio frequencies, and studying them has led to significant discoveries of exoplanets, gravitational waves, and fundamental physics theories. An ongoing research area is the source of pulsar emission and, in turn, the strange way telescopes see some pulsars. These include intermittent pulsars and Rotating Radio Transients (RRATs) i.e. ones that turn on for some time but remain quiet otherwise. While the study of pulsars stretches back to 1967, a more contemporary discovery is that of Fast Radio Bursts (FRBs). The discovery in 2007 led to a burgeoning field in radio astronomy, which has enticed many current-generation telescopes. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is among the bank of telescopes that have been commissioned to find FRBs. This thesis addresses the development and deployment of a novel pipeline for finding new pulsars from galactic and extragalactic single-pulse events. We employ the vast astronomical database collected by the aptly named the CHIME/FRB collaboration over 29 months. The majority of the work was to sort through the CHIME/FRB database for RFI and known pulsars before implementing an unsupervised machine learning algorithm, DBSCAN. DBSCAN made clusters of transient astronomical events which are checked against known pulsars in extant catalogs before being followed up by a second CHIME backend instrument, CHIME/Pulsar. The process has led to 144 candidates, with 12 confirmed new pulsars. Many of the pulsars discovered are RRATs, objects that are atypical for a pulsar in that the pulsed emission is sporadic and intermittent. The continued study of RRATs have the potential to elucidate their intermittency and, by extension, the emission mechanism for pulsars. Thus adding to the current ~120 known RRATs will enable pulsar astronomers to make more substantial claims regarding the estimated ~10⁵ RRATs in the Milky Way Galaxy.
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