[1] George Washington Univ, Dept Phys, Washington, DC 20052 USA
[2] Univ Maryland, Dept Astron, College Pk, MD 20742 USA
[3] NASA, Goddard Space Flight Ctr, Astrophys Sci Div, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA
[4] Univ Leicester, Sch Phys & Astron, Univ Rd, Leicester LE1 7RH, Leics, England
[5] Rice Univ, Dept Phys & Astron, MS 108,6100 Main St, Houston, TX 77251 USA
[6] Univ Washington, Dept Astron, DIRAC Inst, 3910 15th Ave NE, Seattle, WA 98195 USA
[7] Open Univ Israel, Dept Nat Sci, POB 808, IL-4353701 Raanana, Israel
[8] Open Univ Israel, Astrophys Res Ctr Open Univ ARCO, POB 808, IL-4353701 Raanana, Israel
[9] Univ Cape Town, Dept Astron, Private Bag X3, ZA-7701 Rondebosch, South Africa
[10] South African Astron Observ, POB 9, ZA-7935 Cape Town, South Africa
[11] Southern African Large Telescope, POB 9, ZA-7935 Cape Town, South Africa
[12] Univ Free State, Dept Phys, POB 339, ZA-9300 Bloemfontein, South Africa
[13] Univ Maryland, Joint Space Sci Inst, College Pk, MD 20742 USA
[14] Sabanci Univ, Fac Engn & Nat Sci, TR-34956 Istanbul, Turkiye
[15] Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA
[16] NASA, Ctr Res & Explorat Space Sci & Technol, GSFC, Greenbelt, MD 20771 USA
[17] Catholic Univ Amer, 620 Michigan Ave NE, Washington, DC 20064 USA
[18] CALTECH, Cahill Ctr Astrophys, 1216 East Calif Blvd, Pasadena, CA 91125 USA
[19] Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA
[20] SRON Netherlands Inst Space Res, Niels Bohrweg 4, NL-2333 CA Leiden, Netherlands
[21] Univ Amsterdam, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands
[22] Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USA
[23] NASA, CRESST II & Xray Astrophys Lab, GSFC, Greenbelt, MD 20771 USA
[24] Univ Maryland Baltimore Cty, Dept Phys, 1000 Hilltop Circle, Baltimore, MD 21250 USA
[25] Harvard & Smithsonian, Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA
[26] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA
[27] Univ Roma Tor Vergata, Dept Phys, Via Ric Sci, I-00100 Rome, Italy
[28] Univ Amsterdam, Anton Pannekoek Inst, Postbus 94249, NL-1090 GE Amsterdam, Netherlands