1. Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México , Av. Universidad s/n, 62210 Cuernavaca, Mor., México
2. University Nice-Sophia Antipolis , CNRS, Observatoire de la Côte d’Azur, Laboratoire LAGRANGE, CS 34229, F-06304 Nice Cedex 4, France
3. Faculty of Mathematics and Physics, Astronomical Institute, Charles University , V Holešovičách 747/2, 180 00 Prague 8, Czech Republic