1. University of Lyon, UCB Lyon 1, CNRS/IN2P3, IP2I Lyon 69622, France
2. Department of Astronomy, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa
3. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany