[1] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[2] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[3] Max Planck Inst Astrophys, D-85741 Garching, Germany
[4] Univ Porto, Ctr Astrofis, P-4150762 Oporto, Portugal
[5] CNRS, Inst Astrophys Paris, F-75914 Paris, France
[6] CALTECH, Dept Astron, Pasadena, CA 91125 USA
[7] Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA
[8] Princeton Univ Observ, Princeton, NJ 08544 USA
[9] Carnegie Inst Sci, Carnegie Observ, Pasadena, CA 91101 USA
[10] Univ Tokyo, Inst Cosm Ray Res, Kashiwa, Chiba 2778582, Japan
[11] Apache Point Observ, Sunspot, NM 88349 USA