Affiliation: | 1. Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Universität Tübingen, Sand 1, 72076 Tübingen, Germany;2. Kazan State University, Kremlevskaja Street, 18, Kazan 420008, Russia;3. Ioffe Physical-Technical Institute, Polytekhnicheskaya Street, 26, St. Petersburg 194021, Russia |