[1] Max Planck Inst Astrophys, Karl Schwarzschild Str 1, D-85748 Garching, Germany
[2] Leibniz Inst Astrophys, Sternwarte 16, D-14482 Potsdam, Germany
[3] Univ Cologne, Phys Inst 1, Zulpicher Str 77, D-50937 Cologne, Germany
[4] Czech Acad Sci, Astron Inst, Bocni 2 1401-1, CZ-14100 Prague 4, Czech Republic
[5] Charles Univ Prague, Fac Math & Phys, Astron Inst, V Holesovickach 2, CZ-18000 Prague 8, Czech Republic
[6] Heidelberg Univ, Zentrum Astron, Inst Theoret Astrophys, Albert Ueberle Str 2, D-69120 Heidelberg, Germany
[7] Heidelberg Univ, Interdisziplinares Zentrum Wissensch Rechnen, Neuenheimer Feld 205, D-69120 Heidelberg, Germany