1. Department of Physics, Florida Atlantic University, 777 Glades Rd, Boca Raton, FL 33431, USA
2. Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
3. Department of Astronomy & Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
4. The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101, USA
5. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
6. Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA
7. Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK