[1] Rochester Inst Technol, Dept Phys, Rochester, NY 14623 USA
[2] Heidelberg Univ, Zentrum Astron, Astron Rech Inst, D-69120 Heidelberg, Germany
[3] Natl Akad Nauk Ukrainy, Holovna Astron Observ, UA-03680 Kiev, Ukraine
[4] Rochester Inst Technol, Dept Comp Sci, Rochester, NY 14623 USA