2016A&A...596A..77G

We spectroscopically re-observed the gravitational lens system SDSS J1339+1310 using OSIRIS on the GTC. We also monitored the r-band variability of the two quasar images (A and B) with the LT over 143 epochs in the period 2009-2016. These new data in both the wavelength and time domains have confirmed that the system is an unusual microlensing factory. The CIV emission line is remarkably microlensed, since the microlensing magnification of B relative to that for A, µ_BA, reaches a value of 1.4 (∼0.4mag) for its core. Moreover, the B image shows a red wing enhancement of CIV flux (relative to A), and µ_BA=2 (0.75mag) for the CIV broad-line emission. Regarding the nuclear continuum, we find a chromatic behaviour of µ_BA, which roughly varies from ∼5 (1.75mag) at 7000Å to ∼6 (1.95mag) at 4000Å. We also detect significant microlensing variability in the r band, and this includes a number of microlensing events on timescales of 50-100d. Fortunately, the presence of an intrinsic 0.7mag dip in the light curves of A and B, permitted us to measure the time delay between both quasar images. This delay is Δt_AB=47⁺⁵_–6d (1σ confidence interval; A is leading), in good agreement with predictions of lens models.