Gravitational lens system SDSS J1339+1310: microlensing factory and time delay^⋆

¹ Departamento de Física Moderna, Universidad de Cantabria, Avda. de Los Castros s/n, 39005 Santander, Spain
e-mail: goicol@unican.es
² Institute for Radiophysics and Electronics, National Academy of Sciences of Ukraine, 12 Proskura St., 61085 Kharkov, Ukraine
e-mail: vshal@ukr.net

Received: 25 April 2016
Accepted: 8 September 2016

Abstract

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 C iv emission line is remarkably microlensed, since the microlensing magnification of B relative to that for A, μ_BA, reaches a value of 1.4 (~0.4 mag) for its core. Moreover, the B image shows a red wing enhancement of C iv flux (relative to A), and μ_BA = 2 (0.75 mag) for the C iv broad-line emission. Regarding the nuclear continuum, we find a chromatic behaviour of μ_BA, which roughly varies from ~5 (1.75 mag) at 7000 Å to ~6 (1.95 mag) at 4000 Å. We also detect significant microlensing variability in the r band, and this includes a number of microlensing events on timescales of 50–100 d. Fortunately, the presence of an intrinsic 0.7 mag 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_-6 d (1σ confidence interval; A is leading), in good agreement with predictions of lens models.