1. School of Physics, Trinity College Dublin, The University of Dublin , Dublin 2 , Ireland
2. Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL , UK
3. DTU Space, National Space Institute, Technical University of Denmark , Elektrovej 327, DK-2800 Kgs. Lyngby , Denmark
4. Department of Physics and Astronomy, Northwestern University , 2145 Sheridan Rd, Evanston, IL 60208 , USA
5. Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 1800 Sherman Ave, Evanston, IL 60201 , USA
6. Department of Physics and Earth Science, University of Ferrara , via Saragat 1, I-44122 Ferrara , Italy
7. INFN , Sezione di Ferrara, via Saragat 1, I-44122 Ferrara , Italy
8. INAF , Osservatorio Astronomico d’Abruzzo, via Mentore Maggini snc, I-64100 Teramo , Italy
9. MIT-Kavli Institute for Astrophysics and Space Research , 77 Massachusetts Ave., Cambridge, MA 02139 , USA
10. Department of Particle Physics and Astrophysics, Weizmann Institute of Science , 234 Herzl St, Rehovot 7610001 , Israel
11. Astrophysics Research Institute, Liverpool John Moores University , 146 Brownlow Hill, Liverpool L3 5RF , UK
12. Caltech Optical Observatories, California Institute of Technology , Pasadena, CA 91125 , USA
13. Division of Physics, Mathematics and Astronomy, California Institute of Technology , Pasadena, CA 91125 , USA
14. Institut für Physik, Humboldt-Universität zu Berlin , D-12489 Berlin , Germany
15. Deutsches Elektronen Synchrotron DESY , Platanenallee 6, D-15738 Zeuthen , Germany
16. The Oskar Klein Centre, Department of Physics, Stockholm University, Albanova University Center , SE-106 91 Stockholm , Sweden
17. The Oskar Klein Centre, Department of Astronomy, Stockholm University , AlbaNova University Center, SE-106 91 Stockholm , Sweden
18. Las Cumbres Observatory , 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575 , USA
19. Department of Astronomy, University of California , Berkeley, CA 94720-3411 , USA
20. DIRAC Institute, Department of Astronomy, University of Washington , 3910 15th Avenue NE, Seattle, WA 98195 , USA
21. IPAC, California Institute of Technology , 1200 E. California Blvd, Pasadena, CA 91125 , USA
22. LPNHE , CNRS/IN2P3, Sorbonne Université, Université Paris-Cité, Laboratoire de Physique Nucléaire et de Hautes Énergies, F-75005 Paris , France