We report the study of an ” Einstein Cross ” configuration first identified in a set of HST images by \citet Cerny .
Deep spectroscopic observations obtained at the Spanish 10.4m GTC telescope , allowed us to demonstrate the lens nature of the system , that consists of a Lyman-break galaxy , not a QSO as is usually the case , at z = 3.03 lensed by a galaxy at z=0.556 .
Combining the new spectroscopy with the archival HST data , it turns out that the lens is an elliptical galaxy with M _ { V } = -21.0 , effective radius 2.8 kpc and stellar velocity dispersion \sigma =208 \pm 39 km/sec .
The source is a Lyman break galaxy with Ly \alpha luminosity \sim L ^ { * } at that redshift .
From the modeling of the system , performed by assuming a singular isothermal ellipsoid ( SIE ) with external shear , we estimate that the flux source is magnified about 4.5 times , and the velocity dispersion of the lens is \sigma _ { SIE } = 197.9 _ { -1.3 } ^ { +2.6 } km s ^ { -1 } , in good agreement with the value derived spectroscopically .
This is the second case known of an Einstein cross of a Lyman-break galaxy .