1. Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, FL 32306, USA
2. Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
3. Department of Astronomy , University of Washington, Box 351580, Seattle, WA 98195, USA
4. The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St, Pasadena, CA 91101, USA
5. School of Physics, Trinity College Dublin, The University of Dublin, Dublin, Ireland
6. Department of Physics & Astronomy, Vanderbilt University, 6301 Stevenson Center Lane, Nashville, TN 37235, USA
7. Department of Physics, Fisk University, 1000 17th Avenue N., Nashville, TN 37208, USA