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We present the first VLT near-IR observations of a gravitationally lensedquasar, using adaptive optics and laser guide star. These observations can beconsidered as a test bench for future systematic observations of lensed quasarswith adaptive optics, even when bright natural guide stars are not available inthe nearby field. With only 14 minutes of observing time, we derived veryaccurate astrometry of the quasar images and of the lensing galaxy, with 0.05\arcsec spatial resolution, comparable to the Hubble Space Telescope (HST). Incombination with deep VLT optical spectra of the quasar images, we use ouradaptive optics images to constrain simple models for the mass distribution ofthe lensing galaxy. The latter is almost circular and does not need any strongexternal shear to fit the data. The time delay predicted for SDSS0806+2006,assuming a singular isothermal ellipsoid model and the concordance cosmology,is Delta t \simeq 50 days. Our optical spectra indicate a flux ratio betweenthe quasar images of A/B=1.3 in the continuum and A/B=2.2 in both the MgII andin the CIII] broad emission lines. This suggests that microlensing affects thecontinuum emission. However, the constant ratio between the two emission linesindicates that the broad emission line region is not microlensed. Finally, wesee no evidence of reddening by dust in the lensing galaxy.

A sharp look at the gravitationally lensed quasar SDSS J0806+2006 with Laser Guide Star Adaptive Optics