Searching for Fast Radio Transients with SKA Phase 1

Abstract

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.

A Multi-Beam Radio Transient Detector With Real-Time De-Dispersion Over a Wide Dm Range

“…In the less common case where each antenna points to a different patch of sky, referred to as a "fly's eye" observing mode, all beams across the antenna array have different pointing centres and therefore remain uncombined. In-depth discussions of these methods and their suitability to ASKAP, SKA and other interferometric telescopes are presented in Cordes [2007]; D'Addario [2010]; Macquart [2011]; Colegate & Clarke [2011]. For the Tardis system, we have chosen to combine antenna beams incoherently for the following reasons.…”

“…From these data we derive a period of 0.71454 s, slightly larger than the published value, which we attribute to a slowing down of the pulsar's rotation since the published measurement (1968). [Colegate & Clarke, 2011;Trott et al, 2013].…”

The square kilometre array and the transient universe

“…There is a more detailed discussion of some of the computing requirements presented in Smits et al [1]. Discussions on how to further make optimizations between sensitivity and field of view for transient searches, using the different observing modes, such as sub-arraying, fly's eye and trading beams for bandwidth, are presented in Colegate & Clarke [2] and Macquart [3].…”

SKA Studies of the Radio Transient Universe

“…For a coherent combination of the element in the SKA1 core, the event rate is less by a factor of ~5 (SKA1-low) and ~157 (dishes). Refer to [5] for details.…”

“…Colegate and Clarke [5] have produced a summary (Table 1) of recent or forthcoming fast transients surveys, summarizing the expected detection rate on an "event rate per beam" basis, a measure allowing the processing efficiency and cost of transient survey strategies to be compared and optimized. In some cases both coherent and incoherent modes are possible and a representative performance for each case is noted.…”