1. Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Väisäläntie 20, FI-21500 Piikkiö, Finland
2. Anton Pannekoek Institute of Astronomy, University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam, the Netherlands
3. Space Research Institute of the Russian Academy of Sciences, Profsoyuznaya Str. 84/32, Moscow 117997, Russia
4. Moscow Institute of Physics and Technology, Moscow region, Dolgoprudnyi 141701, Russia
5. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA, UK
6. Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden
7. Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA