A pilot ASKAP survey for radio transients towards the Galactic Centre

Abstract

ABSTRACT We present the results of a radio transient and polarization survey towards the Galactic Centre, conducted as part of the Australian Square Kilometre Array Pathfinder Variables and Slow Transients pilot survey. The survey region consisted of five fields covering $\sim 265\, {\rm deg}^2$ (350○ ≲ l ≲ 10○, |b| ≲ 10○). Each field was observed for 12 min, with between 7 and 9 repeats on cadences of between one day and four months. We detected eight highly variable sources and seven highly circularly polarized sources (14 unique sources in total). Seven of these sources are known pulsars including the rotating radio transient PSR J1739–2521 and the eclipsing pulsar PSR J1723–2837. One of them is a low-mass X-ray binary, 4U 1758–25. Three of them are coincident with optical or infrared sources and are likely to be stars. The remaining three may be related to the class of Galactic Centre Radio Transients (including a highly likely one, VAST J173608.2–321634, that has been reported previously), although this class is not yet understood. In the coming years, we expect to detect ∼40 bursts from this kind of source with the proposed 4-yr VAST survey if the distribution of the source is isotropic over the Galactic fields.