Exploring the Transient Radio Sky with ASKAP

Abstract

Many types of astronomical objects show variability at radio wavelengths. While several dedicated transient surveys at other wavelengths have already yielded fruitful results, there are only a few transient surveys at radio wavelengths.

In this thesis, we explored a range of radio transient phenomena with the Australian Square Kilometre Array Pathfinder (ASKAP). In Chapter 2, we present the results of a radio transient and polarisation survey towards the Galactic Centre, conducted as part of the ASKAP Variables and Slow Transients (VAST) pilot survey. As part of the search, we identified a highly-variable, highly-polarised source, ASKAP J173608.2-321635. In Chapter 3, we present detailed follow-up observations of this source. We used a range of facilities over a wide frequency range (from radio to X-ray) to investigate the nature of the source. However, there is no type of source that can fully explain the observational properties of the source. The properties of the source indicate that this could be a newly discovered Galactic Centre Radio Transient (GCRT), whose nature is still unknown. In Chapter 4, we explored the capability of ASKAP to detect fast radio bursts from neutron star mergers. We simulated the slew time of ASKAP for different scenarios and found that the chance of such a detection in coming years would be low. However, with the upgrade of the gravitational wave detector network in the next few years, we suggest that it will be more likely to make such detections.

In conclusion, the work in this thesis demonstrates the ability of ASKAP to explore a variety of transient phenomena. Further transient surveys with ASKAP, MeerKAT, the Deep Synoptic Array (DSA), the next-generation VLA (ngVLA) and the Square Kilometre Array (SKA) will enable us to have comprehensive understanding of the radio transient sources population, and may reveal new types of sources in the future.