1. Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
2. Department of Physics, University of Milan Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy
3. Ècole Normale Supérieure de Paris-Saclay 4 Avenue des Sciences, F-91190 Gif-sur-Yvette, France
4. Kapteyn Astronomical Institute, University of Groningen, Landleven 12, NL-9747 AD Groningen, the Netherlands
5. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
6. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
7. Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230 Saint-Genis-Laval, France
8. Observatoire de Genève, Université de Genève, 51 Chemin de Pégase, CH-1290 Versoix, Switzerland