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.
Search and identification of transient and variable radio sources using MeerKAT observations: a case study on the MAXI J1820+070 field
Many transient and variable sources detected at multiple wavelengths are also observed to vary at radio frequencies. However, these samples are typically biased towards sources that are initially detected in wide-field optical, X-ray, or gamma-ray surveys. Many sources that are insufficiently bright at higher frequencies are therefore missed, leading to potential gaps in our knowledge of these sources and missing populations that are not detectable in optical, X-rays, or gamma-rays. Taking advantage of new state-of-the-art radio facilities that provide high-quality wide-field images with fast survey speeds, we can now conduct unbiased surveys for transient and variable sources at radio frequencies. In this paper, we present an unbiased survey using observations obtained by MeerKAT, a mid-frequency (∼GHz) radio array in South Africa’s Karoo Desert. The observations used were obtained as part of a weekly monitoring campaign for X-ray binaries (XRBs) and we focus on the field of MAXI J1820+070. We develop methods to efficiently filter transient and variable candidates that can be directly applied to other data sets. In addition to MAXI J1820+070, we identify four likely active galactic nuclei, one source that could be a Galactic source (pulsar or quiescent XRB) or an AGN, and one variable pulsar. No more »
- Publication Date:
- NSF-PAR ID:
- 10376219
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 517
- Issue:
- 2
- Page Range or eLocation-ID:
- p. 2894-2911
- ISSN:
- 0035-8711
- Publisher:
- Oxford University Press
- Sponsoring Org:
- National Science Foundation
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