1. Department of Physics & Astronomy, Louisiana State University , Baton Rouge, LA 70803, USA
2. Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Rm 100, Norman, OK 73019-2061, USA
3. Hamburger Sternwarte , Gojenbergsweg 112, D-21029 Hamburg, Germany
4. Department of Physics, Virginia Tech , Blacksburg, VA 24061, USA
5. Department of Physics, Florida State University , 77 Chieftan Way, Tallahassee, FL 32306, USA