The MAVERIC survey: A catalogue of radio sources in southern globular clusters from the Australia Telescope Compact Array

TL;DR

The MAVERIC survey conducted deep radio observations of 26 southern globular clusters, cataloging 1285 sources, revealing populations of compact objects and new binary candidates, thus providing insights into cluster demographics.

Contribution

This study provides the first comprehensive radio source catalog for 26 globular clusters, identifying potential new compact binaries and advancing understanding of cluster populations.

Findings

Detected 1285 radio sources across 26 clusters

Identified significant populations in 7 clusters

Discovered a candidate ultracompact black hole binary

Abstract

Radio continuum observations offer a new window on compact objects in globular clusters compared to typical X-ray or optical studies. As part of the MAVERIC survey, we have used the Australia Telescope Compact Array to carry out a deep (median central noise level of approximately 4 microJy per beam) radio continuum survey of 26 southern globular clusters at central frequencies of 5.5 and 9.0 GHz. This paper presents a catalogue of 1285 radio continuum sources in the fields of these 26 clusters. Considering the surface density of background sources, we find significant evidence for a population of radio sources in seven of the 26 clusters, and also identify at least 11 previously known compact objects (6 pulsars and 5 X-ray binaries). While the overall density of radio continuum sources with 7.25-GHz flux densities greater than about 20 microJy in typical globular clusters is relatively low, the survey has already led to the discovery of several exciting compact binaries, including a candidate ultracompact black hole X-ray binary in 47 Tuc. Many of the unclassified radio sources near the centres of the clusters are likely to be true cluster sources, and multi-wavelength follow-up will be necessary to classify these objects and better understand the demographics of accreting compact binaries in globular clusters.