1. Department of Physics and Astronomy, University of Turku , Vesilinnantie 5, Turku FI-20014 , Finland
2. Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL , UK
3. Institute of Cosmology and Gravitation, University of Portsmouth , Portsmouth PO1 3FX , UK
4. Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH , UK
5. School of Physics and Astronomy, Monash University , Clayton VIC 3800 , Australia
6. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife , Spain
7. School of Physics and Astronomy, University of Leicester, University Road , Leicester LE1 7RH, UK
8. Armagh Observatory and Planetarium, College Hill , Armagh BT61 9DG, UK
9. National Astronomical Research Institute of Thailand , 260 Moo 4, T. Donkaew, A. Maerim, Chiangmai 50180 , Thailand
10. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL , UK
11. Departamento de Astrofísica, Univ. de La Laguna , E-38206 La Laguna, Tenerife , Spain
12. School of Physics and Astronomy, University of Birmingham , Birmingham B15 2TT , UK
13. Department of Astrophysics, American Museum of Natural History , Central Park West and 79th Street, New York, NY 10024-5192 , USA
14. School of Physics, Kane Building, University College Cork , Cork , Ireland
15. Department of Astrophysics/IMAPP, Radboud University , Postbus 9010, NL-6500 GL Nijmegen , The Netherlands
16. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester , Manchester M13 9PL, UK
17. School of Sciences, European University Cyprus , Diogenes street, Engomi, 1516 Nicosia , Cyprus
18. Centre for Astrophysics Research, University of Hertfordshire , College Lane, Hatfield AL10 9AB , UK