  CSL-1 is a peculiar object (R.A._{2000}= 12h 23m 30.5"; Dec_{2000}= -12deg
38' 57.0") which, for its photometric and spectroscopic properties, is possibly
the first case of gravitational lensing by a cosmic string. In this paper we
present additional evidences, based on medium-high resolution VLT + FORS1
observations, that the spectra of the two components of CSL-1 are identical
within a confidence level higher than 99.9% and the velocity difference of the
two components is consistent with zero. This result adds further confidence to
the interpretation of the system as a true lens.

Astrophysics