A pilot ASKAP survey for radio transients towards the Galactic Centre

TL;DR

This pilot survey using ASKAP aimed to detect radio transients and polarisation signals near the Galactic Centre, discovering various known pulsars, potential new transient sources, and providing insights into their properties and distribution.

Contribution

First radio transient survey of the Galactic Centre with ASKAP, identifying known pulsars, potential new transients, and characterizing their polarisation and variability.

Findings

Detected 8 highly variable sources and 7 highly circularly-polarised sources.

Identified known pulsars and potential Galactic Centre Radio Transients.

Projected detection of ~40 bursts over four years with the VAST survey.

Abstract

We present the results of a radio transient and polarisation 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 $\sim265\,{\rm deg}^2$ ($350^\circ\lesssim l\lesssim10^\circ$, $\vert b\vert \lesssim 10^\circ$). Each field was observed for 12\,minutes, 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-polarised 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 $\sim$40 bursts from this kind of source with the proposed four-year VAST survey if the distribution of the source is isotropic over the Galactic fields.