1. GEPI, Observatoire de Paris, Paris Sciences et Lettres, CNRS , Place Jules Janssen, F-92195 Meudon, France
2. School of Physical Sciences, University of Chinese Academy of Sciences , Beijing 100049, P. R. China
3. CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Beijing 100101, China
4. Institut d’Astrophysique de Paris (UMR7095: CNRS & Sorbonne Université) , 98 bis Bd Arago, F-75014 Paris, France
5. Leibniz-Institut fuer Astrophysik Potsdam (AIP) , An der Sternwarte 16, D-14482 Potsdam Germany
6. CREF, Centro Ricerche Enrico Fermi , Via Panisperna 89A, I-00184 Roma, Italy