[1] New York Univ Abu Dhabi, POB 129188, Abu Dhabi, U Arab Emirates
[2] New York Univ Abu Dhabi, Ctr Astro Particle & Planetary Phys CAP3, Abu Dhabi, U Arab Emirates
[3] Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany
[4] Alma Mater Studiorum Univ Bologna, Dipartimento Fis & Astron, Via Piero Gobetti 93-2, I-40129 Bologna, BO, Italy
[5] INAF Osservatorio Astron Bologna, Via Piero Gobetti 93-3, I-40129 Bologna, BO, Italy
[6] Ist Nazl Fis Nucl, Sez Bologna, Viale Berti Pichat 6-2, I-40127 Bologna, BO, Italy