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

TL;DR

This study confirms SDSS J1339+1310 as an active microlensing system with variable magnification affecting emission lines and continuum, and measures a time delay of approximately 47 days between its quasar images.

Contribution

The paper provides detailed spectroscopic and photometric analysis of the microlensing effects and accurately measures the time delay in this gravitational lens system.

Findings

Microlensing significantly affects C IV emission lines and continuum.

Detected multiple microlensing events on 50-100 day timescales.

Measured a time delay of 47 days between quasar images.

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$-$2016. These new data in both the wavelength and time domains have confirmed that the system is an unusual microlensing factory. The C$\scriptsize{\rm{IV}}$ emission line is remarkably microlensed, since the microlensing magnification of B relative to that for A, $\mu_{\rm{BA}}$, reaches a value of 1.4 ($\sim$ 0.4 mag) for its core. Moreover, the B image shows a red wing enhancement of C$\scriptsize{\rm{IV}}$ flux (relative to A), and $\mu_{\rm{BA}}$ = 2 (0.75 mag) for the C$\scriptsize{\rm{IV}}$ broad-line emission. Regarding the nuclear continuum, we find a chromatic behaviour of $\mu_{\rm{BA}}$, which roughly varies from $\sim$ 5 (1.75 mag) at 7000 \AA\ to $\sim$ 6 (1.95 mag) at 4000 \AA. 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 $\Delta t_{\rm{AB}}$ = 47$^{+5}_{-6}$ d (1$\sigma$ confidence interval; A is leading), in good agreement with predictions of lens models.