1. APC, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, France
2. Gran Sasso Science Institute, Viale Francesco Crispi 7, 67100 L’Aquila, Italy
3. INFN/Laboratori Nazionali del Gran Sasso, Via G. Acitelli 22, Assergi (AQ), Italy
4. INAF/Osservatorio Astrofico di Arcetri, L.go E. Fermi 5, Firenze, Italy