1. Department of Physics and Astronomy, Box 41051, Science Building, Texas Tech University, Lubbock, TX 79409-1051, USA
2. George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, Department of Physics and Astronomy, 4242 TAMU, College Station, TX 77843, USA
3. Department of Physics and Astronomy, Trinity University, San Antonio, TX 78212, USA; Eureka Scientific, Inc., USA
4. Department of Astronomy, University of Texas at Austin, Austin, TX 78712, USA