VAST: An ASKAP Survey for Variables and Slow Transients

Abstract

The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, an ASKAP survey for Variables and Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP to enable the discovery and investigation of variable and transient phenomena from the local to the cosmological, including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar scintillation, radio supernovae, and orphan afterglows of gamma-ray bursts. In addition, it will allow us to probe unexplored regions of parameter space where new classes of transient sources may be detected. In this paper we review the known radio transient and variable populations and the current results from blind radio surveys. We outline a comprehensive program based on a multi-tiered survey strategy to characterise the radio transient sky through detection and monitoring of transient and variable sources on the ASKAP imaging timescales of 5 s and greater. We also present an analysis of the expected source populations that we will be able to detect with VAST.

Ultra-wideband Detection of 22 Coherent Radio Bursts on M Dwarfs

“…We next calculated the coherent burst duty cycle and expected transient density for the frequency bands of three ongoing or upcoming transient surveys ( Figure 6): VAST (1.13-1.43 GHz;Murphy et al 2013), ThunderKAT L-band (0.9-1.67 GHz; but we used 1-1.67 GHz, the part of the band that overlaps with our frequency coverage), and VLASS (2-4 GHz). We generated these predictions following the same procedure described in the previous section, but using a shorter integration time of 150 sec, enabled by the better sen-sitivity of these bands compared to the 340-480 MHz band considered in the previous section.…”

The square kilometre array and the transient universe

“…The combination of the sophisticated and powerful LOFAR computing platform, the low observing frequency and the dipole-like receiving elements means that these surveys will revolutionize our understanding of the transient radio sky. The other SKA precursor telescopes such as ASKAP and MeerKAT also have planned transient programmes: VAST [32], CRAFT, TRAPUM and ThunderKAT [13], and these will all help pave the way for transient searches with the SKA in both phases. In addition to these new observing projects, there are exciting new developments in detection methods such as multi-moment analysis [33], the Chirpolator and Chimageator [34], millisecond imaging [35] and the use of interferometric closure quantities [36].…”

MKT J170456.2–482100: the first transient discovered by MeerKAT

“…Blind searches for radio transients using interferometers present many challenges, particularly modest field of view (FoV) and limited observing cadence (e.g. Murphy et al 2013;Mooley et al 2016Mooley et al , 2018. With current wide FoV ( 1 square degree) instruments such as MeerKAT (Camilo et al 2018), the Australian Square Kilometer Array Pathfinder (ASKAP; Johnston et al 2008;Schinckel et al 2012), APERTIF (Maan & van Leeuwen 2017), the LOw Frequency Array (LOFAR; van Haarlem et al 2013), and the Murchison Wide Field Array (MWA; Tingay et al 2012), surveying large areas of sky with various cadences and improved sensitivity is now possible.…”