1. Department of Physics and Astronomy, Louisiana State University , 202 Nicholson Hall, Tower Drive, Baton Rouge, LA 70803 , USA
2. Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218 , USA
3. Department of Physics, Durham University, Odgen Centre For Fundamental Physics West, Lower Mountjoy , South Road, Durham DH1 3LE , UK
4. NASA Goddard Space Flight Center , Bldg L40, Greenbelt, MD 20770 , USA