[1] Astronomical Institute, Utrecht University, Princetonplein 5, 3584CC Utrecht, Netherlands
[2] SRON, Laboratory for Space Research, Sorbonnelaan 2, 3584CC Utrecht, Netherlands
[3] Sternwarte, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
[4] Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
[5] Astronomisches Rechen-Institut, Mönchhofstraße 12-14, 69120 Heidelberg, Germany
[6] Main Astronomical Observatory, 27 Academica Zabolotnogo Str., 03680 Kiev, Ukraine
[7] Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, Netherlands
[8] Informatics Institute, University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, Netherlands