MeerTRAP: Searching for radio transients with MeerKAT

  • Mechiel Christiaan Bezuidenhout

Student thesis: Phd

Abstract

Transient astrophysical sources are characterised by the release of vast amounts of energy over a very short period of time, and as such are associated with some of the most energetic environments in existence. The extremely sensitive MeerKAT radio telescope array in the Karoo region of South Africa, itself a precursor to the larger Square-Kilometre Array (SKA), presents an unprecedented look at these sources, and by extension the physical processes that produce them. More TRansients And Pulsars (MeerTRAP) is a European Research Council advanced grant funded project to use commensal MeerKAT observations to search for pulsars and fast radio transients. In this thesis, I describe the discovery of Galactic transient sources using the MeerTRAP single pulse search pipeline, as well as multi-telescope follow-up observing campaigns of these sources. I also discuss novel techniques developed for constraining their positions. To start, I introduce pulsars and radio transients, before discussing approaches towards searching for single pulses from these sources, the MeerKAT radio telescope, and the MeerTRAP real-time, commensal single pulse survey. In Chapter 2 I present the discovery of twelve new Galactic source by MeerTRAP as well as the results of a long-term follow-up campaign of these sources spanning almost two years using three different radio telescopes. Repeat pulses from seven of the sources were detected, enabling us to derive pulse periods for four of the sources. Another four could be localised to approximately arcsecond precision using a novel method I developed for localising single pulses using their S/N values measured in different MeerKAT tied-array beams. Next, I present analysis of long term follow-up observations of MeerTRAP's thirteenth Galactic source, PSR J0901−4046. This radio-emitting neutron star is unique, possessing the longest spin period ever observed in such an object (~75.88 seconds). This places PSR J0901−4046 beyond the putative pulsar "death line", where pulsars are thought to possess too little rotational energy to emit at radio frequencies in various models of pulsar radio emission. PSR J0901−4046 single pulses also exhibit various unusual spectro-temporal-polarimetric features that I explore further in Chapter 3. The discovery of PSR J0901−4046 points to an exciting new frontier of the neutron star parameter space, where any number of sources may exist with spin periods beyond what traditional Fourier transform-based periodicity searches are suited to. Chapter 4 showcases the novel tied-array beam localisation (TABLo) method that we have developed for localising single pulses from pulsars and transients to arcsecond precision without the need to image the field. I provide idealised test cases of its use, as well as real-world examples of its successful employment by multiple different MeerKAT pulsar and transient search projects to aid in follow-up efforts for newly discovered sources. Finally, in Chapter 5 I outline various elaborations on the basic TABLo method that may point the way towards further improvements on the localisation precision, as well as a few additional localisation methods using tied-array beams that may be of use in certain scenarios where TABLo cannot be used.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorBenjamin Stappers (Supervisor) & Patrick Weltevrede (Supervisor)

Keywords

  • Radio astronomy
  • Fast radio transients
  • Pulsars
  • Neutron stars
  • Surveys

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