Discovery of Four Doubly Imaged Quasar Lenses from the Sloan Digital Sky
  Survey
  We report the discovery of four doubly imaged quasar lenses. All the four
systems are selected as lensed quasar candidates from the Sloan Digital Sky
Survey data. We confirm their lensing hypothesis with additional imaging and
spectroscopic follow-up observations. The discovered lenses are SDSS J0743+2457
with the source redshift z_s=2.165, the lens redshift z_l=0.381, and the image
separation theta=1.034", SDSS J1128+2402 with z_s=1.608 and theta=0.844", SDSS
J1405+0959 with z_s=1.810, z_l~0.66, and theta=1.978", and SDSS J1515+1511 with
z_s=2.054, z_l=0.742, and theta=1.989". It is difficult to estimate the lens
redshift of SDSS J1128+2402 from the current data. Two of the four systems
(SDSS J1405+0959 and SDSS J1515+1511) are included in our final statistical
lens sample to derive constraints on dark energy and the evolution of massive
galaxies.
