[1] E Tennessee State Univ, Dept Phys & Astron, Johnson City, TN 37614 USA
[2] Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany
[3] Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland
[4] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA
[5] Swarthmore Coll, Dept Phys & Astron, Swarthmore, PA 19081 USA
[6] Observ Midi Pyrenees, LATT, F-31400 Toulouse, France
[7] Penn State Worthington Scranton, Dept Phys, Dunmore, PA 18512 USA