Searching for Fast Radio Transients with SKA Phase 1

TL;DR

This paper evaluates strategies for detecting fast radio transients with SKA Phase 1, highlighting the effectiveness of incoherent combination and optimal bandwidth, and discusses how search strategies vary with sky direction and source populations.

Contribution

It introduces event rate per unit cost as a new figure of merit for comparing transient survey strategies for radio telescopes, and provides insights into optimal configurations for SKA Phase 1.

Findings

Incoherent combination of antenna signals yields the highest event rate per beam.

A bandwidth of 50-100 MHz is sufficient for extragalactic searches with SKA Phase 1.

Full bandwidth gain is small; search strategy depends on sky direction and source population.

Abstract

The Square Kilometre Array (SKA) provides an excellent opportunity for low cost searches for fast radio transients. The increased sensitivity and field of view of the SKA compared with other radio telescopes will make it an ideal instrument to search for impulsive emission from high energy density events. We present a high-level search use case and propose event rate per unit cost as a figure of merit to compare transient survey strategies for radio telescope arrays; we use event rate per beam formed and searched as a first-order approximation of this measure. Key results are that incoherent (phase insensitive) combination of antenna signals achieves the highest event rate per beam, and that 50-100 MHz processed bandwidth is sufficient for extragalactic searches with SKA Phase 1; the gain in event rate from using the full available bandwidth is small. Greater system flexibility will enable more effective searches, but need not drive the top-level system requirements beyond those already proposed for the SKA. The most appropriate search strategy depends on the observed sky direction and the source population; for SKA Phase 1, low frequency aperture arrays tend to be more effective for extragalactic searches and dishes more effective for directions of increased scatter broadening, such as near the Galactic plane.