[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, POB 129188, Abu Dhabi, U Arab Emirates
[3] Univ Padua, Phys & Astron Dept Galileo Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy
[4] Univ Montreal, Dept Phys, Montreal, PQ H3T 1J4, Canada
[5] Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany
[6] Christian Albrechts Univ Kiel, Inst Theoret Phys & Astrophys, Leibnizstr 15, D-24118 Kiel, Germany
[7] Zhejiang Univ, Zhejiang Univ Purple Mt Observ Joint Res Ctr Astr, Hangzhou 310027, Peoples R China
[8] Purple Mt Observ, 10 Yuan Hua Rd, Nanjing 210034, Peoples R China