1. Escuela de Física, Universidad Industrial de Santander, A. A. 678, Bucaramanga 680002, Colombia
2. Department of Physics and Astronomy, College of Charleston, Charleston, SC 29424, USA
3. Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA 93106, USA
4. Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, PL 00-716 Warsaw, Poland