[1] Fudan Univ, Ctr Field Theory & Particle Phys, Shanghai 200438, Peoples R China
[2] Fudan Univ, Dept Phys, Shanghai 200438, Peoples R China
[3] Univ Groningen, Kapteyn Astron Inst, NL-9747 AD Groningen, Netherlands
[4] Ulugh Beg Astron Inst, Tashkent 100052, Uzbekistan
[5] Eberhard Karls Univ Tubingen, Theoret Astrophys, D-72076 Tubingen, Germany
[6] Tsinghua Univ, Dept Astron, Beijing 100084, Peoples R China
[7] Eberhard Karls Univ Tubingen, Inst Astron & Astrophys, D-72076 Tubingen, Germany