1. Konkoly Observatory, CSFK, Konkoly-Thege M. út 15-17, 1121 Budapest, Hungary
2. Department of Optics & Quantum Electronics, Institute of Physics, University of Szeged, Dóm tér 9, 6720 Szeged, Hungary
3. Institute of Physics, ELTE Eötvös Loránd University, Pázmány Péter Sétány 1/A, 1117 Budapest, Hungary
4. Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA
5. Department of Experimental Physics, Institute of Physics, University of Szeged, Dóm tér 9, 6720 Szeged, Hungary
6. ELKH-SZTE Stellar Astrophysics Research Group, Szegedi út, Kt. 766, 6500 Baja, Hungary
7. Gothard Astrophysical Observatory, ELTE Eötvös Loránd University, 9700 Szombathely, Hungary