1. Department of Astronomy, The University of Cape Town , Private Bag X3, Rondebosch 7701 Cape Town , South Africa
2. High Energy Physics, Cosmology & Astrophysics Theory (HEPCAT) Group, Department of Mathematics & Applied Mathematics, University of Cape Town , 7700 Cape Town , South Africa
3. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester , M13 9PL Manchester , United Kingdom
4. Max-Planck-Institut für Radioastronomie , Auf Hügel 69, D-53121 Bonn , Germany
5. South African Radio Astronomy Observatory (SARAO) , 2 Fir Street, Black River Park, Observatory, 7925 Cape Town
6. INAF-Osservatorio Astronomico di Cagliari , via della Scienza 5, 09047 Selargius (CA) , Italy
7. Centre for Space Research, North-West University , Private Bag X6001, 2520 Potchefstroom , South Africa
8. National Institute for Theoretical and Computational Sciences , (NITheCS), Stellenbosch, 7604 , South Africa
9. Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) , D-30167 Hannover , Germany
10. Leibniz Universität Hannover , D-30167 Hannover , Germany