1. TAPIR, California Institute of Technology , Pasadena, CA 91125, USA
2. Department of Physics, Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology , Cambridge, MA 02139, USA
3. Universität Heidelberg, Zentrum für Astronomie, Institut für theoretische Astrophysik , Albert-Ueberle-Str 2, D-69120 Heidelberg, Germany
4. Center for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA, 02138, USA
5. Max-Planck-Institut für Astrophysik , Karl-Schwarzschild-Str 1, D-85741 Garching, Germany
6. Department of Physics & Astronomy ‘Augusto Righi’, University of Bologna , via Gobetti 93/2, I-40129 Bologna, Italy
7. Department of Astronomy, University of Florida , 211 Bryant Space Sciences Center, Gainesville, FL 32611 USA