1. Department of Physics and Astronomy, Texas Tech University , PO Box 41051, Lubbock, TX 79409, USA
2. Finnish Centre for Astronomy with ESO (FINCA) , Quantum, FI-20014 University of Turku, Finland
3. Center for Astrophysics | Harvard & Smithsonian , 60 Garden St, Cambridge, MA 02138, USA
4. Department of Physics and Astronomy, 20014 University of Turku , Finland
5. Department of Physics, University of California , Santa Barbara, CA 93106, USA
6. Kavli Institute for Theoretical Physics, University of California , Santa Barbara, CA 93106, USA
7. Department of Physics, University of Warwick , Coventry CV4 7AL, UK
8. INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica , Via A. Corti 12, I-20133 Milano, Italy