1. Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK
2. Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary
3. Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica SK-059 60, Slovakia
4. School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK
5. Department of Physics and Astronomy, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK