1. Università di Torino, Dipartimento di Fisica, via P. Giuria 1, I-10125, Torino, Italy
2. Osservatorio Astrofisico di Torino, Istituto Nazionale di Astrofisica (INAF), I-10025 Pino Torinese, Italy
3. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
4. Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, E-08028 Barcelona, Spain
5. Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France
6. GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, F-92190 Meudon, France
7. France Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
8. Institut UTINAM, CNRS UMR6213, Univ. Bourgogne Franche-Comté, OSU THETA Franche-Comté-Bourgogne, Observatoire de Besançon, BP 1615, F-25010 Besançon Cedex, France
9. Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, United Kingdom